1 00:01:30,400 --> 00:01:35,512 Most of the earth is covered by water. 2 00:01:36,138 --> 00:01:38,640 In fact, two-thirds of it is. 3 00:01:39,558 --> 00:01:42,186 And it's only in this generation 4 00:01:42,394 --> 00:01:50,027 that we have been able to move about it with any degree of freedom as I am doing now. 5 00:01:51,069 --> 00:01:58,869 So perhaps it is not surprising that still most of this vast domain 6 00:01:59,036 --> 00:02:00,787 is still unexplored. 7 00:02:01,955 --> 00:02:05,334 And in the geographical sense, 8 00:02:06,251 --> 00:02:10,339 the surface of the sea, the floor of the sea, 9 00:02:11,340 --> 00:02:14,927 is even more varied than the surface of the land. 10 00:02:32,736 --> 00:02:37,783 To see just how varied it is, let's take an imaginary journey across the Pacific 11 00:02:37,950 --> 00:02:42,246 starting in the west where the ocean is deeper than anywhere else on the globe: 12 00:02:42,412 --> 00:02:44,122 The Mariana trench. 13 00:02:44,998 --> 00:02:51,213 The bottom of this immense valley seven miles below the surface is grooved by deep faults. 14 00:02:51,922 --> 00:02:53,966 If Mount Everest rose from the bottom, 15 00:02:54,258 --> 00:02:58,512 its summit would still be beneath 7,000 feet of water. 16 00:02:59,555 --> 00:03:04,518 Down at the very bottom, the water pressure is some seven tons per square inch, 17 00:03:04,852 --> 00:03:08,105 the temperature is close to freezing, and it's pitch-dark, 18 00:03:08,522 --> 00:03:10,941 for it is far beyond the reach of sunlight. 19 00:03:25,372 --> 00:03:30,919 As we climb up out of the trench, we move onto a plain covered with reddish mud. 20 00:03:38,218 --> 00:03:44,057 A few hills rise from it, but there are still some 20,000 feet of water above us. 21 00:03:45,976 --> 00:03:48,729 Travel eastwards over these plains for 1,000 miles, 22 00:03:48,896 --> 00:03:51,982 and we reach a range of fantastic mountains. 23 00:03:52,441 --> 00:03:55,277 Their summits are covered by a white deposit like snow, 24 00:03:55,485 --> 00:03:57,654 composed of the limestone skeletons 25 00:03:57,821 --> 00:04:02,117 of microscopic organisms that have drifted down from the surface. 26 00:04:02,701 --> 00:04:07,789 Before they reach the lower slopes, the water pressure becomes so great they dissolve. 27 00:04:10,834 --> 00:04:16,423 Currents sweeping up from the south pile the sand into dunes 150 feet high 28 00:04:16,590 --> 00:04:21,929 which advance slowly across the sea floor as dunes do in a desert on land. 29 00:04:26,767 --> 00:04:31,980 In places, the sand is littered with metallic lumps, some as big as cannon balls: 30 00:04:32,481 --> 00:04:37,236 Manganese that under these pressures has precipitated out from the salty water. 31 00:04:48,455 --> 00:04:53,794 After a journey of 4,000 miles, we reach the biggest mountains of all. 32 00:04:54,169 --> 00:04:57,631 These are the flanks of the great volcanic islands of Hawaii. 33 00:04:58,048 --> 00:05:01,176 Their sides are steeper than any mountain on land 34 00:05:01,343 --> 00:05:04,888 for they are never eroded by frost or by rivers armed with gravel. 35 00:05:05,222 --> 00:05:09,184 They rise from the sea floor 15,000 feet to the surface 36 00:05:09,351 --> 00:05:12,563 and continue for an almost equal height above it, 37 00:05:12,855 --> 00:05:16,984 so they can truly be reckoned the highest mountains in the world. 38 00:05:19,570 --> 00:05:21,947 As we climb up their sides towards the surface, 39 00:05:22,155 --> 00:05:26,410 we return once more to light and to abundant life. 40 00:05:34,126 --> 00:05:38,672 Life began in sunlit waters like these some 3,000 million years ago, 41 00:05:39,006 --> 00:05:42,217 and creatures very similar to those ancient primeval organisms 42 00:05:42,426 --> 00:05:45,846 still flourish in shallow seas all over the world. 43 00:05:46,972 --> 00:05:53,270 Feather stars like these waved their tentacles long before any fish appeared, 44 00:05:53,437 --> 00:05:57,107 at a time when the land was still bare of life of any kind. 45 00:06:05,866 --> 00:06:09,244 Horseshoe crabs come from an equally antique stock. 46 00:06:09,536 --> 00:06:13,165 Fossils have been found in rocks 600 million years old. 47 00:06:14,249 --> 00:06:15,792 Most of their relatives have died out. 48 00:06:16,043 --> 00:06:21,215 These are the lonely survivors of a widespread and successful group. 49 00:06:40,734 --> 00:06:44,196 Even older, indeed among the first of all living things, 50 00:06:44,404 --> 00:06:47,824 microscopic plants encased in shells of limestone. 51 00:06:48,367 --> 00:06:53,121 They use sunshine to build, from simple chemicals in the sea water, their own tissue. 52 00:06:53,831 --> 00:06:57,334 This act of photosynthesis, transforming mineral into vegetable, 53 00:06:57,501 --> 00:07:00,295 is the basis of all life in the sea. 54 00:07:06,009 --> 00:07:07,761 A myriad of creatures feed on them. 55 00:07:08,095 --> 00:07:14,017 Some are tiny animals, scarcely bigger than the plants that they waft into their mouths. 56 00:07:21,108 --> 00:07:24,945 This floating community of plants and animals is the plankton. 57 00:07:25,279 --> 00:07:28,740 Its members move endlessly through the blue seas. 58 00:07:28,949 --> 00:07:34,538 Many are fragile constructions of jelly that would collapse without the support of water. 59 00:07:45,299 --> 00:07:48,510 Some are colonial, several feet long. 60 00:07:57,769 --> 00:08:01,607 They call this Venus's girdle. It's two feet across. 61 00:08:01,815 --> 00:08:05,110 Light catches in the beating hairs that ripple over its body 62 00:08:05,277 --> 00:08:08,155 as it moves slowly through the water. 63 00:08:11,366 --> 00:08:14,912 The animals of the plankton, all those that can't photosynthesise, 64 00:08:15,078 --> 00:08:20,667 sweep up the tiny plants and other edible particle in many different ways. 65 00:08:23,337 --> 00:08:28,842 This one extends a forest of long tentacles in which smaller organisms get entangled. 66 00:08:31,261 --> 00:08:35,015 This, transparent as glass, trails stinging thread 67 00:08:35,182 --> 00:08:38,268 and pulls them in whenever they catch something. 68 00:08:53,200 --> 00:08:55,744 Worms actively pursue their prey. 69 00:09:04,545 --> 00:09:09,299 Creatures from many families of animals have representatives in this community. 70 00:09:09,550 --> 00:09:13,387 Some are permanent members, some only temporary, 71 00:09:13,554 --> 00:09:17,099 joining it when they are young larvae and drifting great distances 72 00:09:17,307 --> 00:09:21,854 before they grow up, change shape and settle down to a more static life. 73 00:09:22,354 --> 00:09:27,484 But all are ultimately dependent on the tiny microscopic plants. 74 00:09:38,328 --> 00:09:41,707 There is another way in which the drifting particles of food can be gathered. 75 00:09:41,957 --> 00:09:45,919 Instead of moving with the current, you stay fixed to the rocks 76 00:09:46,086 --> 00:09:49,214 and allow the currents to bring food to you. 77 00:09:49,673 --> 00:09:53,385 That is the technique used by anemones and many other creatures. 78 00:09:56,221 --> 00:10:01,560 As the water sweeps by, the particles it carries stick to the waving tentacles. 79 00:10:13,363 --> 00:10:18,160 All kinds of creatures live in this fashion. This is a sea cucumber. 80 00:10:25,125 --> 00:10:27,753 And this, a basket star. 81 00:10:39,723 --> 00:10:43,310 The water brings not only food but vital oxygen. 82 00:10:43,519 --> 00:10:46,271 If it doesn't bring it fast enough, it can be speeded 83 00:10:46,480 --> 00:10:49,316 by pulsing as these coral polyps are doing. 84 00:10:55,155 --> 00:10:59,868 It's not only simple creatures like anemones and corals that filter currents. 85 00:11:00,118 --> 00:11:03,747 Other more complex animals have also taken to doing so. 86 00:11:03,956 --> 00:11:07,835 This is a remote relative of the shrimps that has settled down on its back, 87 00:11:08,001 --> 00:11:13,382 grown a protective shell and fishes for the passing particles with its feet 88 00:11:22,558 --> 00:11:23,934 It's a barnacle. 89 00:11:28,188 --> 00:11:31,692 Some crabs also rely on the currents to bring them meals, 90 00:11:31,859 --> 00:11:35,279 and pluck them from the water with tiny pincers. 91 00:11:40,409 --> 00:11:46,456 But the biggest of all filter-feeders propel themselves gently through the surface waters. 92 00:11:53,422 --> 00:11:56,216 A manta ray, 18 feet across. 93 00:11:56,633 --> 00:11:58,010 It often feeds at night 94 00:11:58,177 --> 00:12:02,181 when dense swarms of the plankton move up towards the surface. 95 00:12:02,681 --> 00:12:06,727 The water is channelled into its mouth by the blades on the sides of its head, 96 00:12:06,894 --> 00:12:11,190 then passes through filters in the slits in the sides of its throat. 97 00:12:18,655 --> 00:12:23,410 The basking shark gathers the same sort of food in a similar way. 98 00:12:23,994 --> 00:12:29,625 It grows even bigger than the manta: 40 feet long and four tons in weight. 99 00:12:32,753 --> 00:12:38,175 Idling through the water, it filters over 1,000 tons of water every hour. 100 00:12:50,187 --> 00:12:55,901 And even bigger still, in fact, the biggest of all fish: The whale shark. 101 00:12:57,694 --> 00:13:01,823 This mountain of a creature can be up to 50 feet long. 102 00:13:14,503 --> 00:13:20,968 Other, more normal-sized fish live on and around it. Some collect its refuse. 103 00:13:30,519 --> 00:13:36,483 Others pick off morsels that get stuck in its tiny teeth in a mouth six feet wide. 104 00:13:38,318 --> 00:13:43,991 It's an astonishing proof of how sustaining and how abundant the plankton must be. 105 00:13:55,711 --> 00:14:00,757 But of course, not all sharks live on plankton or are quite so amiable. 106 00:14:03,719 --> 00:14:07,431 These are grey reef sharks, about six feet long. 107 00:14:19,860 --> 00:14:25,365 It's some consolation to know that those sharks don't normally attack human beings. 108 00:14:25,741 --> 00:14:31,163 Their prey is usually small fish or predators. 109 00:14:31,872 --> 00:14:39,963 And indeed, when one looks at them, it is not so much their danger that comes into your mind 110 00:14:40,172 --> 00:14:42,174 as their extraordinary beauty. 111 00:14:42,841 --> 00:14:45,886 They are so perfectly streamlined, 112 00:14:46,053 --> 00:14:49,348 every curve of their body, every curve of their fin 113 00:14:49,515 --> 00:14:57,189 precisely matching the shape that is needed to glide through the water with the least struggle 114 00:14:57,689 --> 00:14:59,233 Most beautiful things. 115 00:15:01,443 --> 00:15:06,990 Sharks belong to a very ancient family that evolved this shape some 400 million years ago. 116 00:15:07,282 --> 00:15:11,370 But soon after they appeared, another group of fish established itself. 117 00:15:13,747 --> 00:15:17,292 These have skeletons of bone, not gristle as the sharks have, 118 00:15:17,459 --> 00:15:20,587 and they have two swimming aids that the sharks lack: 119 00:15:20,921 --> 00:15:23,173 Swim bladders that give them buoyancy 120 00:15:23,382 --> 00:15:26,510 and paired fins that can twist in all directions 121 00:15:26,718 --> 00:15:29,304 and so give them great manoeuvrability in the water. 122 00:15:30,013 --> 00:15:34,935 These bony fish are the ones which today dominate the seas. 123 00:16:02,838 --> 00:16:07,092 Among them are the most powerful of all hunters in the sea: The tuna. 124 00:16:07,509 --> 00:16:10,721 When hunting, they can swim faster than any other fish. 125 00:16:10,888 --> 00:16:16,727 Some say nearly 70 miles an hour, faster even than a cheetah can run on land. 126 00:16:17,978 --> 00:16:21,148 But the fish's dominance of the sea didn't go unchallenged. 127 00:16:21,356 --> 00:16:27,237 Ten million years ago, warm-blooded creatures from the land invaded the sea, mammals, 128 00:16:27,404 --> 00:16:30,199 and they became equally streamlined. 129 00:17:01,188 --> 00:17:03,899 Dolphins and killer whales are descended 130 00:17:04,107 --> 00:17:09,363 from four-footed, land-living, air-breathing mammals that were flesh-eaters. 131 00:17:09,863 --> 00:17:14,368 In the sea, they lost their limbs but not their taste for meat, nor their teeth. 132 00:17:14,701 --> 00:17:18,914 Indeed, one of the family that lives only in the ice-strewn waters of the Arctic 133 00:17:19,081 --> 00:17:23,001 has grown one of its teeth to an extraordinary length. 134 00:17:33,095 --> 00:17:35,931 These are narwhals, and they are all males, 135 00:17:36,098 --> 00:17:40,227 for only the male produces the tusk, up to nine feet long. 136 00:17:44,273 --> 00:17:48,318 These without tusks are females, one with a calf. 137 00:17:49,027 --> 00:17:51,238 And these are young males. 138 00:17:57,744 --> 00:18:00,956 No one knows for certain what purpose the tusk serves, 139 00:18:01,165 --> 00:18:03,792 but it seems likely that it is used in courtship. 140 00:18:04,168 --> 00:18:07,796 That is confirmed by the fact that very rarely indeed 141 00:18:07,963 --> 00:18:12,009 males have been glimpsed, as here, fencing with one another. 142 00:18:40,245 --> 00:18:45,501 The best view that most of us can get for most of the time of most kinds of whales 143 00:18:45,667 --> 00:18:51,089 is a brief glimpse as the animal comes to the surface to snatch a breath, 144 00:18:51,340 --> 00:18:56,887 but that's not the case with the beluga, these beautiful white whales. 145 00:18:57,262 --> 00:19:02,809 Up here in the Canadian Arctic, they come during those brief weeks 146 00:19:02,976 --> 00:19:05,521 when the ice goes away from these shores, 147 00:19:05,729 --> 00:19:09,775 and assemble in vast numbers in this bay. 148 00:19:10,108 --> 00:19:13,820 There are hundreds, sometimes as many as a thousand. 149 00:19:21,703 --> 00:19:26,583 We don't really know why they come here, nor what they do now that they are here. 150 00:19:26,834 --> 00:19:30,754 Maybe there is some kind of specially attractive food in these shallow waters, 151 00:19:30,963 --> 00:19:35,551 for they seem to stir up the gravelly bottom of the bay. 152 00:19:36,176 --> 00:19:40,639 Perhaps there is valuable food for youngsters or nursing mothers, 153 00:19:40,931 --> 00:19:44,810 for many that come are females with babies a few months old, 154 00:19:45,018 --> 00:19:47,729 swimming skilfully in their mother's slipstream. 155 00:19:48,021 --> 00:19:52,693 Whatever it is that they do here, they seem to be enjoying themselves hugely. 156 00:19:58,657 --> 00:20:02,202 And they haven't lost their mammalian habit of communicating by sound. 157 00:20:02,661 --> 00:20:06,540 So vocal are they that they are sometimes called sea canaries. 158 00:20:15,465 --> 00:20:18,969 The most recent family to colonise the sea, also mammals, 159 00:20:19,136 --> 00:20:21,680 were descended from bear-like creatures. 160 00:20:22,514 --> 00:20:24,474 The walrus and its cousin the seals 161 00:20:24,641 --> 00:20:30,063 are not so fully adapted to life in the sea as the whales, but they haven't been there so long. 162 00:20:38,238 --> 00:20:43,494 They haven't lost their feet as the whales have, nor do they spend all their lives in the water. 163 00:20:47,456 --> 00:20:51,251 They come ashore to give birth and they often haul themselves out to rest. 164 00:20:51,710 --> 00:20:53,879 Nonetheless, they are superb swimmers. 165 00:21:03,805 --> 00:21:08,810 So, in the 3,000 million years since living organisms first appeared in the sea, 166 00:21:08,977 --> 00:21:12,940 the oceans have acquired a population of immense diversity, 167 00:21:13,106 --> 00:21:16,026 from single-celled microscopic plants 168 00:21:16,193 --> 00:21:19,780 to advanced and complex highly intelligent mammals. 169 00:21:20,280 --> 00:21:24,868 Indeed, there are more different groups of animals living in the sea than there are on land. 170 00:21:28,497 --> 00:21:31,792 The oceans were the birthplace and the nursery of life, 171 00:21:31,959 --> 00:21:34,586 and they are still its main residence. 172 00:22:31,310 --> 00:22:33,312 But the sea is not uniform. 173 00:22:33,562 --> 00:22:36,607 Just as land has different, specialised environments 174 00:22:36,773 --> 00:22:41,236 inhabited by creatures that occur nowhere else, so does the sea. 175 00:22:41,904 --> 00:22:47,826 The coral lagoon is a world of its own. Corals are very demanding in their requirements. 176 00:22:48,076 --> 00:22:52,289 They must have good light, clear, unpolluted water and warmth, 177 00:22:52,456 --> 00:22:56,126 and they find this in the tropics, 178 00:22:56,376 --> 00:23:00,714 particularly around the small islands that are the summits of submarine mountains. 179 00:23:00,964 --> 00:23:04,927 There, they flourish so well that they grow outwards into the clear blue water, 180 00:23:05,093 --> 00:23:10,390 building on top of their own skeletons to form wide, shallow lagoons. 181 00:23:15,354 --> 00:23:19,816 The variety of corals is immense. Some are soft and rubbery, 182 00:23:19,983 --> 00:23:25,155 others are hard and slightly flexible, like a horn But most are stony. 183 00:23:25,989 --> 00:23:31,787 The organisms that build these structures, ton upon ton, occupy only the outer skin. 184 00:23:32,162 --> 00:23:37,042 The rest is dead. As they develop, the little organisms branch, 185 00:23:37,209 --> 00:23:40,337 and the particular way they do so determines the shape of the colony, 186 00:23:40,504 --> 00:23:46,552 forming antlers and organ pipes, whips and fans, vases and buttons. 187 00:24:01,233 --> 00:24:05,779 If the jungle is the place on land 188 00:24:06,238 --> 00:24:12,452 where there are the greatest number and the greatest variety of life, 189 00:24:13,203 --> 00:24:19,877 then this, the coral reef, is surely the jungle of the sea. 190 00:24:20,669 --> 00:24:22,504 The number, the variety, 191 00:24:22,671 --> 00:24:30,387 the sheer beauty of all these myriad fish, corals and anemones, is quite breathtaking. 192 00:24:33,265 --> 00:24:40,230 Of course, the tiny anemone-like creatures that build these fans and fronds of coral 193 00:24:40,439 --> 00:24:41,940 are themselves animals. 194 00:24:42,774 --> 00:24:52,075 But within their tissues, there are tiny granules which are algae, plants, 195 00:24:52,451 --> 00:25:00,459 and it's they that harness the sunshine and use it to build living tissue. 196 00:25:01,001 --> 00:25:04,838 And onto these plates and branches of coral 197 00:25:05,005 --> 00:25:08,759 come a wide variety of creatures to browse. 198 00:25:10,761 --> 00:25:13,555 Some, like the parrotfish, bite off chunks. 199 00:25:13,805 --> 00:25:18,519 Others pick off little organisms and particles with the utmost delicacy. 200 00:25:37,204 --> 00:25:39,957 The tides, surging in and out of the lagoon, 201 00:25:40,123 --> 00:25:45,128 bring in regular supplies of fresh oxygenated water and fresh food. 202 00:25:45,462 --> 00:25:51,134 Angler fish sit in the current waiting patiently, like all fishermen, for whatever turns up. 203 00:25:51,426 --> 00:25:56,139 Even such specialised fish as these exist on the reef in several different versions. 204 00:25:56,390 --> 00:26:01,103 There's this lemon-yellow one that angles with a movable spine on its forehead. 205 00:26:08,443 --> 00:26:11,572 Little reef fish find it an irresistible bait. 206 00:26:20,789 --> 00:26:24,710 More prey to be angled for by the decoy fish. 207 00:26:33,552 --> 00:26:38,932 A dorsal fin patterned with a false eye and mouth so that it looks like a little fish 208 00:26:39,141 --> 00:26:44,146 and may attract other small fish or possibly predatory ones. 209 00:26:45,480 --> 00:26:48,817 This one is the wrong way round. Its spines would stick in the mouth. 210 00:26:53,822 --> 00:26:54,990 That's better. 211 00:26:55,991 --> 00:26:58,785 One of the fastest actions in the animal world. 212 00:27:02,331 --> 00:27:05,584 And the angler, perhaps to prevent a second fish arriving 213 00:27:05,751 --> 00:27:07,586 before it has digested the first, 214 00:27:07,753 --> 00:27:10,881 changes colour so that the lure vanishes. 215 00:27:17,804 --> 00:27:20,933 In the reef, there are many species with many ways of life. 216 00:27:21,225 --> 00:27:23,477 Just take the crustaceans, for example. 217 00:27:23,852 --> 00:27:26,146 Hermit crabs live by scavenging. 218 00:27:26,396 --> 00:27:30,651 Often, they share the shells they have commandeered as a home with anemones. 219 00:27:32,277 --> 00:27:35,572 The anemones benefit by picking up bits of the crab's meal 220 00:27:35,739 --> 00:27:40,285 and give the crab in return a certain protection with their stinging tentacles. 221 00:27:42,371 --> 00:27:45,916 This crab actually uses a particular kind of anemone as a weapon, 222 00:27:46,208 --> 00:27:48,710 wearing one on each claw like boxing gloves. 223 00:27:51,547 --> 00:27:54,466 This one tries to put on a sponge like an overcoat. 224 00:27:54,716 --> 00:27:58,846 It's rather overdoing things, for the brown jersey it's wearing 225 00:27:59,054 --> 00:28:01,807 is also a sponge, and a well-established one. 226 00:28:02,182 --> 00:28:04,268 But the arrangement will suit both parties. 227 00:28:04,476 --> 00:28:09,022 The crab gets the camouflage and the sponge may benefit from the crab's crumbs. 228 00:28:15,904 --> 00:28:18,407 Crabs and their relations, the lobsters and shrimps, 229 00:28:18,574 --> 00:28:20,909 are found from top to bottom of the reef. 230 00:28:21,326 --> 00:28:25,581 Big ones like this lobster prowl openly through the coral branches. 231 00:28:31,837 --> 00:28:36,592 Little ones like the mantis shrimp are rather more cautious and build themselves tunnels. 232 00:28:46,977 --> 00:28:49,646 If the coral reef is the equivalent of the jungle, 233 00:28:49,855 --> 00:28:55,444 maybe these waving beds of kelp in the cold Atlantic waters off the coast of Norway 234 00:28:55,611 --> 00:28:59,114 are like the dark evergreen forests of the north, 235 00:28:59,364 --> 00:29:04,870 bitterly cold, dense and uniform, and swept by raging gales. 236 00:29:25,933 --> 00:29:29,686 Bleak though the kelp forest may seem, there are riches here, 237 00:29:29,853 --> 00:29:31,897 and eider duck know it. 238 00:29:44,660 --> 00:29:48,831 The eiders settle in flocks on the surface of the water above the kelp forest, 239 00:29:49,039 --> 00:29:53,836 and they are almost as adept in flying through the water as they are through the air. 240 00:30:12,312 --> 00:30:15,440 This is what they seek: Mussels. 241 00:30:25,325 --> 00:30:30,122 Eiders are true creatures of the sea, seldom, if ever, visiting fresh water. 242 00:30:30,330 --> 00:30:35,169 They prefer to fish for mussels on an ebb tide when the water is low, 243 00:30:35,377 --> 00:30:39,381 but they can stay below water for a minute or more, 244 00:30:39,548 --> 00:30:42,926 and dive down to 50 feet below the surface. 245 00:30:53,353 --> 00:30:57,816 The streaming current causes great problems to the fish of the kelp forest. 246 00:30:58,066 --> 00:31:00,736 Simply maintaining a position there is a struggle. 247 00:31:00,903 --> 00:31:05,157 The lumpsucker does it with modified fins on its underside, 248 00:31:05,449 --> 00:31:10,829 and gets such a firm grip that it is extremely difficult to pull it off. 249 00:31:11,038 --> 00:31:13,540 Its young develop suckers at a very early age 250 00:31:13,707 --> 00:31:18,879 and sometimes fix themselves to their father, who ferries them off to deeper waters. 251 00:31:22,216 --> 00:31:25,177 Kelp grows in coastal waters all round the world, 252 00:31:25,344 --> 00:31:28,263 and in the seaweed forests of southern Australia 253 00:31:28,430 --> 00:31:32,601 lives one of the most extravagantly camouflaged of all fish. 254 00:31:42,528 --> 00:31:45,447 Other fish appear to be completely deceived. 255 00:31:45,697 --> 00:31:48,200 This small one, itself with a false eye 256 00:31:48,367 --> 00:31:51,119 so that it is difficult to tell whether it is coming or going, 257 00:31:51,286 --> 00:31:57,334 lives in these green leafy tatters as though they were real plants, but they're not. 258 00:31:57,584 --> 00:32:02,297 They're all part of the elaborate costume of the leafy seadragon. 259 00:32:34,454 --> 00:32:36,790 The dragon is a kind of a seahorse, 260 00:32:36,957 --> 00:32:42,296 as you can see if you disentangle its main body from its extraordinary outgrowths. 261 00:32:42,629 --> 00:32:48,218 Like its relatives, it has a tiny mouth with which it picks up small shrimps 262 00:32:48,385 --> 00:32:52,931 that ill-advisedly take shelter in what appears to be floating weed. 263 00:33:28,300 --> 00:33:32,012 As well as its forests, the sea has its deserts. 264 00:33:32,387 --> 00:33:38,352 Over vast areas of the ocean floor, there is nothing but shifting wastes of sand. 265 00:33:40,187 --> 00:33:44,566 It seems as lifeless as a desert on land in the heat of the day. 266 00:33:48,612 --> 00:33:53,367 An occasional fish wanders over the rippled surface as though lost. 267 00:33:56,119 --> 00:33:59,164 Here and there, a sea urchin levers itself along, 268 00:33:59,373 --> 00:34:03,961 extracting what nutriment it can find from particles within the sand. 269 00:34:09,383 --> 00:34:14,888 The goatfish looks for the same sort of thing, using sensitive barbels on its chin. 270 00:34:21,979 --> 00:34:26,400 To build a home or a shelter in sand demands special techniques. 271 00:34:27,067 --> 00:34:30,737 Garden eels cement grains together with mucus to form a tube 272 00:34:30,904 --> 00:34:35,492 in which they cling with their tails while collecting plankton with their mouths. 273 00:34:37,411 --> 00:34:41,290 Bulldozer shrimps and a goby cooperate to build a shared tunnel, 274 00:34:41,498 --> 00:34:44,126 using coral rubble to prop up the roof. 275 00:35:05,564 --> 00:35:09,651 The bladefish can improvise a shelter on the spur of the moment. 276 00:35:18,660 --> 00:35:20,954 There are two very different reasons for hiding. 277 00:35:21,163 --> 00:35:24,708 The bladefish does it to get out of trouble. 278 00:35:28,504 --> 00:35:30,547 This little cuttlefish does it... 279 00:35:32,925 --> 00:35:35,135 ...in order to cause trouble. 280 00:35:49,942 --> 00:35:52,069 The prey is a shrimp. 281 00:36:20,305 --> 00:36:24,226 And the cuttlefish has the shrimp firmly in its tentacles. 282 00:36:38,907 --> 00:36:43,203 The floating pastures of plankton on which so many ocean-going fish depend 283 00:36:43,412 --> 00:36:47,332 must live in the surface waters within the reach of sunshine. 284 00:36:47,833 --> 00:36:53,005 The coral lagoon and the kelp forests only flourish where good light reaches the bottom. 285 00:36:53,463 --> 00:36:57,009 But light can't penetrate much beyond 350 feet, 286 00:36:57,176 --> 00:37:01,305 and most of the ocean floor lies far deeper that that. 287 00:37:10,272 --> 00:37:14,443 Even quite near the surface you have to take your own light with you. 288 00:37:25,787 --> 00:37:28,081 Fish, too, carry lights. 289 00:37:33,921 --> 00:37:37,090 The flashlight fish use theirs to find their food 290 00:37:37,299 --> 00:37:42,513 and to maintain contact like other species in deeper water. 291 00:37:44,056 --> 00:37:48,852 Their batteries are little colonies of bacteria living in a pouch beneath the fish's eye 292 00:37:49,061 --> 00:37:52,272 that give off light as a by-product of their chemistry, 293 00:37:52,439 --> 00:37:57,986 and the fish turns its lights off and on by raising and lowering a flap of skin. 294 00:38:02,908 --> 00:38:08,330 At greater depths, giant amphipods, primitive relatives of the horseshoe crabs, 295 00:38:08,497 --> 00:38:10,123 plod along the bottom. 296 00:38:10,958 --> 00:38:14,294 Very little is known about these strange creatures. 297 00:38:37,484 --> 00:38:40,988 Even at 3,000 feet down there is life. 298 00:38:41,363 --> 00:38:45,909 Almost all the creatures here feed on dead bodies that fall from above. 299 00:38:46,160 --> 00:38:49,079 The eel-like hagfish, which have no jaws, 300 00:38:49,288 --> 00:38:52,749 knot themselves against the carcass to get a better hold. 301 00:39:07,347 --> 00:39:12,311 Bigger fish grip with their teeth and spin, tearing off strips of the flesh. 302 00:39:14,897 --> 00:39:17,399 The smaller particles drifting down from the surface 303 00:39:17,566 --> 00:39:20,944 are collected by deep-sea stars and smaller fish. 304 00:39:21,195 --> 00:39:25,866 It is here that all the nutrients produced by decay finally collect as ooze. 305 00:39:26,200 --> 00:39:30,496 The very deepest parts of the ocean lie below the paths of currents, 306 00:39:30,662 --> 00:39:34,958 so the water is not only black and cold but almost still. 307 00:39:37,461 --> 00:39:42,549 The weird tripod fish perches on its extended fins and its tail. 308 00:39:48,514 --> 00:39:54,144 Even in the deepest place of all, the Mariana trench, seven miles down, there is life. 309 00:39:55,062 --> 00:39:57,981 Shrimps are slowly picking clean the skeleton of a fish 310 00:39:58,148 --> 00:40:02,736 that may have taken months to drift down to these still depths. 311 00:40:09,576 --> 00:40:13,372 But at the surface of the sea, the water is never still. 312 00:40:26,718 --> 00:40:31,306 Storms whip it up into great waves which may travel for hundreds of miles 313 00:40:31,473 --> 00:40:34,643 before, eventually, they crash into the coasts. 314 00:40:45,696 --> 00:40:48,323 The water in these waves doesn't travel far, 315 00:40:48,490 --> 00:40:53,453 but circulates more or less in the same place while the wave itself moves on. 316 00:40:54,496 --> 00:40:58,083 But that circulation is of crucial importance to the creatures of the sea, 317 00:40:58,250 --> 00:41:04,631 for it is this that allows the waters of the sea to absorb the vital oxygen from the air above. 318 00:41:46,340 --> 00:41:49,343 But deep currents do move through the oceans. 319 00:41:49,718 --> 00:41:51,803 They are created by the spin of the earth 320 00:41:52,012 --> 00:41:55,098 which gives the waters at the equator a westward drift, 321 00:41:55,307 --> 00:42:01,271 and by the sun which warms these equatorial waters and sends them away to the poles. 322 00:42:01,939 --> 00:42:07,945 This produces vast ocean-wide eddies that replicate the whirlpools of tidal races, 323 00:42:08,111 --> 00:42:12,324 but do so on a scale that is thousands of miles across. 324 00:42:17,579 --> 00:42:20,791 In the Pacific, the equatorial current divides, 325 00:42:20,999 --> 00:42:24,336 and in the south it flows down as far as New Zealand. 326 00:42:27,214 --> 00:42:30,551 In the Indian Ocean, the southern system is almost circular. 327 00:42:30,801 --> 00:42:33,929 The northern has to swirl around the great triangle of India. 328 00:42:36,974 --> 00:42:40,853 In the Atlantic, the north-flowing current is called the Gulf Stream, 329 00:42:41,019 --> 00:42:46,066 and it encloses, in the centre of the ocean, as all these great whirlpools do, 330 00:42:46,233 --> 00:42:49,236 an area where the waters are almost still. 331 00:42:51,530 --> 00:42:56,285 On their surface float rafts of weed. It never roots but floats for ever, 332 00:42:56,451 --> 00:43:01,874 rocked sufficiently by the swell to prevent its topmost fronds from drying out in the sun. 333 00:43:10,382 --> 00:43:11,466 The Portuguese sailors, 334 00:43:11,675 --> 00:43:16,638 looking at the little bladders that keep it afloat called them sargasso: Grapes. 335 00:43:17,181 --> 00:43:18,974 This is the Sargasso Sea. 336 00:43:19,474 --> 00:43:24,229 Like every other region within the oceans, it has its own specialised inhabitants. 337 00:43:26,565 --> 00:43:31,570 Small fish shelter in its fronds and are closely disguised to match them, 338 00:43:31,737 --> 00:43:36,658 and swimming crabs clamber up and rest on top of the floating mats. 339 00:43:37,576 --> 00:43:42,623 But the Sargasso is one of the least fertile stretches of water in all the oceans. 340 00:43:43,040 --> 00:43:46,960 Since no currents feed into it, it receives no nutrients 341 00:43:47,127 --> 00:43:50,130 and its clear waters are largely barren. 342 00:43:55,594 --> 00:43:58,055 But patches of it occasionally break away. 343 00:44:01,892 --> 00:44:04,144 Between the Gulf Stream and the North American coast 344 00:44:04,353 --> 00:44:08,899 there are cores of cold Sargasso water surrounded by warm circulating currents 345 00:44:09,066 --> 00:44:14,154 formed when the Gulf Stream meanders and nips off a segment of the Sargasso, 346 00:44:14,321 --> 00:44:16,949 complete with its weed and populations of animals. 347 00:44:17,366 --> 00:44:20,536 These warm core-rings, a hundred or so miles across, 348 00:44:20,744 --> 00:44:24,873 drift down the coast until they lose their momentum and their warmth, 349 00:44:25,040 --> 00:44:28,377 break up and are swept away again by the Gulf Stream. 350 00:44:30,337 --> 00:44:35,008 The Gulf Stream continues northwards along the coast to Newfoundland. 351 00:44:37,261 --> 00:44:41,890 Here, off these bleak fogbound beaches, it creates an area of seas 352 00:44:42,099 --> 00:44:47,062 that might be seen as one of the most fertile and productive places on the entire globe, 353 00:44:47,354 --> 00:44:50,941 a place where the full potential richness of the ocean is realised, 354 00:44:51,150 --> 00:44:56,363 and where animals of all kinds come to harvest it. 355 00:45:00,784 --> 00:45:05,873 The warm water of the Gulf Stream is accompanied by steady warm breezes. 356 00:45:06,456 --> 00:45:12,838 And just about here, it meets a cold current coming down from the Arctic, 357 00:45:13,130 --> 00:45:18,260 and where the warm breezes meet the icy breath of the Arctic, 358 00:45:18,719 --> 00:45:21,930 they shed their moisture and form these fogs. 359 00:45:22,264 --> 00:45:27,019 And where the two currents meet, the waters churn and swirl, 360 00:45:27,227 --> 00:45:31,857 and bring up rich nutrients from the bottom of the sea. 361 00:45:32,191 --> 00:45:34,985 Now, it so happens that just off this coast 362 00:45:35,194 --> 00:45:38,864 there is an underwater plateau where the water is so shallow 363 00:45:39,031 --> 00:45:43,785 that the sun or the light can get almost always to the bottom, 364 00:45:44,161 --> 00:45:49,166 and so the floating plants of the sea are always within the range of light, 365 00:45:49,333 --> 00:45:54,796 and they're fed eternally by these swirling currents bringing up nutrients. 366 00:45:55,589 --> 00:46:00,052 So the plants flourish, and on them come great shoals of fish 367 00:46:00,219 --> 00:46:03,263 which breed and spawn in such numbers 368 00:46:03,430 --> 00:46:07,559 that at times the waters seem almost to boil with them. 369 00:46:08,810 --> 00:46:13,106 These are capelin, a small fish related to the European smelt. 370 00:46:13,482 --> 00:46:15,901 They feed on the plankton in the surface waters, 371 00:46:16,068 --> 00:46:20,155 and in May they gather in vast shoals to spawn. 372 00:46:20,531 --> 00:46:22,241 Some will do so offshore, 373 00:46:22,449 --> 00:46:26,662 but some go to extraordinary trouble to lay their eggs out of water 374 00:46:26,870 --> 00:46:29,373 where they will be safe from other hungry fish. 375 00:46:32,918 --> 00:46:36,129 The shoals come closer and closer inshore. 376 00:46:44,721 --> 00:46:48,559 Each female capelin can produce 10,000 eggs. 377 00:46:48,934 --> 00:46:53,647 Each wave brings in tens of thousands of fish again and again. 378 00:46:54,148 --> 00:46:56,984 The number of eggs defies any computation. 379 00:46:57,276 --> 00:47:01,405 They pile up in banks, as solid as sand along the high-water mark. 380 00:47:03,657 --> 00:47:08,162 Having spawned, all the males and most of the females die. 381 00:47:22,968 --> 00:47:25,679 The richness that the capelin gathered from the plankton 382 00:47:25,846 --> 00:47:30,225 and converted into their own flesh is now gathered by birds. 383 00:47:32,102 --> 00:47:35,981 Shearwaters gorge themselves on the dying and the dead. 384 00:47:48,577 --> 00:47:52,623 Gannets dive between the scavengers, taking the live fish. 385 00:47:58,545 --> 00:48:03,926 And still the capelin come in. Even before they get to the shallows, they are hunted. 386 00:48:06,887 --> 00:48:12,684 Herds of seals come up to the Grand Banks specially at this time to share in the bonanza. 387 00:49:01,567 --> 00:49:05,154 And here, too, come the biggest hunters of all. 388 00:49:10,951 --> 00:49:12,578 Humpbacked whales. 389 00:49:23,505 --> 00:49:29,636 With each upward lunge, the whale takes in tons of water and thousands of capelin. 390 00:49:36,810 --> 00:49:40,272 With a mouthful in its jaws, it brings forward its tongue, 391 00:49:40,481 --> 00:49:44,735 squirts out surplus water through the filter plate that hang from its upper jaw 392 00:49:44,902 --> 00:49:47,154 and swallows the tiny fish. 393 00:50:11,470 --> 00:50:15,098 The whales have developed a way of concentrating the capelin shoals 394 00:50:15,307 --> 00:50:19,269 so that they will get the greatest number of fish in a single mouthful. 395 00:50:19,937 --> 00:50:21,772 It's called bubble-netting. 396 00:50:22,439 --> 00:50:26,193 Those white areas are huge masses of bubbles. 397 00:50:26,902 --> 00:50:29,655 The whales dive deep below the swarming capelin 398 00:50:29,822 --> 00:50:35,202 and start a slow, spiralling swim upwards, blowing gusts of bubbles as they rise. 399 00:50:35,494 --> 00:50:38,789 The capelin, frightened by the circular curtain of bubbles, 400 00:50:38,956 --> 00:50:42,376 rush inwards and form a dense, confused shoal. 401 00:50:42,626 --> 00:50:47,798 The whale rises up in the middle, jaws agape, and engulfs the lot. 402 00:50:58,684 --> 00:51:02,271 After a few short weeks, the spawning orgy of the capelin is over. 403 00:51:02,688 --> 00:51:06,775 Their bodies lie in vast drifts awaiting the processes of decay 404 00:51:06,942 --> 00:51:09,403 which will return their nutrients to the waters, 405 00:51:09,820 --> 00:51:14,908 but even before they disperse, other bodies appear: Dead squid. 406 00:51:16,368 --> 00:51:19,955 Nobody knows where they have come from, or why they have died in such numbers, 407 00:51:20,164 --> 00:51:23,333 but these blizzards of bodies appear most years in July, 408 00:51:23,500 --> 00:51:27,629 and are a sign that shoals of the living animals are about to arrive. 409 00:51:39,016 --> 00:51:41,977 They will bite any small, moving thing. 410 00:51:42,269 --> 00:51:47,858 To catch them, you don't even need bait. They simply impale themselves on a naked hook, 411 00:51:48,025 --> 00:51:53,947 so that most summers, fishing villages on the Newfoundland coast go jigging for squid, 412 00:51:54,156 --> 00:51:56,366 hauling them out by the thousands. 413 00:52:11,131 --> 00:52:14,927 As they're hooked, they puff out clouds of squid ink. 414 00:52:24,269 --> 00:52:27,523 Hundreds of tons of them are despatched every year to Japan 415 00:52:27,731 --> 00:52:30,067 where they are a much-prized food. 416 00:52:36,740 --> 00:52:42,996 Mackerel also come to the Grand Banks by the million to feed on small plankton-feeding fish 417 00:52:44,915 --> 00:52:48,252 They're netted by the ton by fleets of factory ships, 418 00:52:48,460 --> 00:52:51,713 and their rich flesh is valued all over the world. 419 00:52:53,841 --> 00:52:57,302 But even the Grand Banks are not inexhaustible. 420 00:52:58,679 --> 00:53:04,226 During this century, man has fished so skilfully, so intensively, so unrelentingly, 421 00:53:04,434 --> 00:53:08,021 that he has begun to change the pattern of life in the sea. 422 00:53:08,355 --> 00:53:11,942 Some kinds of fish have been forced to change their habits, 423 00:53:12,151 --> 00:53:14,945 others have been driven close to the edge of extinction. 424 00:53:15,320 --> 00:53:20,701 This little port in Newfoundland, close to what was once the richest of all seas, 425 00:53:20,868 --> 00:53:24,121 now brings in fewer catches, 426 00:53:24,288 --> 00:53:29,960 and modern fish-processing plants like that one are mostly standing idle. 427 00:53:30,294 --> 00:53:35,924 So man has changed the sea, just as he's changed almost every environment in the world. 428 00:53:36,133 --> 00:53:37,718 But he's done something else, too. 429 00:53:38,051 --> 00:53:40,345 He's created new environments, 430 00:53:40,512 --> 00:53:44,308 environments of brick and concrete, and chromium and plastic. 431 00:53:45,017 --> 00:53:48,228 It's the latest of the world's environments, 432 00:53:48,437 --> 00:53:52,274 and the ways in which plants and animals have adapted to live in them.