Ninety per cent of the planet’s living space—and biodiversity—is under water. And there are only five manned craft on Earth that can get to the bottom of it. What they find is both terrifying and alluring. J.M. Ledgard probes the weird world of the submersible

From INTELLIGENT LIFE magazine, Summer 2008

Imagine you are on a beach in Zanzibar, facing the Indian Ocean, and your intent is not to go across, not to paddle, but to go down into the ocean. You walk out under the palm trees, carrying snorkel and flippers. The shore is white sand, it burns the soles of your feet. Several thousand crabs scuttle into tiny holes before you. You wade out into aquamarine waters, soapy, the temperature of blood. At first there is nothing, only patterned sand, then a gathering of kelp, an eel, some milky jellies, a wall of rock with fissures where the sharks sometimes make it through, finally, an opening out onto a coral reef. This is the most munificent garden, you think. A sea garden. There are fronds and tendrils, angel fish, thorny puffer fish inflating in the shadows, rays moving somnolent on the chalky bottom, a luminous purple starfish. Most of all there is light. This is a part of the world you know. The sunshine falls in thick shafts, bending, illuminating the coral. Swim farther out, under the churning surf, and your world falls away.

The waters there are darker and greener, also colder. You are still at the surface, and no matter your intent, your instinct is to stay at the surface, remaining afloat, except perhaps in the sardine season, when the shoals move up from Antarctic waters, and you might swim down a few metres, ten, 20 at the most, to see the dolphins parting the clouds of sardines. Even at 20 metres, the world you know begins to recede. The sun hardens and contracts in the murk, as a pupil contracts in the light. The colours bleach. There is no red. If you cut yourself, your blood will look black. The sea water itself changes, it ceases to be the stuff of sea gardens, but becomes massive, corrosive, anti-human. There is a pressing-in at your ears, sinuses and temples. You look down through your mask. There is only liquid obsidian, a bottomless pit, in every folklore the place of the drowned and the damned. Sailors call it Davy Jones's locker. Even oceanographers run out of epithets. They regularly call it the eternal darkness. It is starless, crushing, terrifying, yet alluring. What the hell is down there?

For a start, 91% of the planet's living space and 90% of its biodiversity. The Earth is really the Ocean. "Il faut aller voir," commanded the French oceanographer Jacques Cousteau. "We must go and see."

Going and seeing requires a manned submersiblea tiny craft designed to deal with the tremendous pressures of the deep, pressures so violent that the finest jet of water, entering at depth, can slice a body in two. Submarines can't venture into the deep. They operate at shallow depths: if they go down too far, they implode.

Only rich nations can afford submersibles and even they balk at the cost. There are only five submersibles in the world's fleet capable of diving below 3,000 metres. Among them are Alvin, operated out of the Woods Hole Oceanographic Institution in Massachusetts; France's Nautile, named for Jules Verne's Nautilus; the twin Mir I and Mir II submersibles of the Russian Academy in St Petersburg; and Japan's Shinkai, sailing out of Yokosuka. The operating depths of these craft range up to 6,500 metres, 680 atmospheres, putting 96% of the ocean floor within the range of aquanauts. None is capable of matching the feat of Jacques Piccard and Don Walsh, who, in 1960, touched down on the Challenger Deep of the Marianas Trench in the bathyscaphe Triesteat 10,911 metres the deepest point on our planet.

The history of deep ocean exploration is short. The first forays were made off Bermuda in 1930. An American naturalist, William Beebe, put out a challenge sponsored by the New York Zoological Society for an underwater capsule elegant in its simplicity. A wealthy compatriot, Otis Barton, invented the bathyspherea steel ball with windows of fused quartz, attached to a surface ship by a cable (above). In 1932, released like a yo-yo from the barge above, the bathysphere, with Beebe and Barton crammed inside, reached a depth of 923 metres.

Dangling in depths only the drowned had previously plumbed and which no artist or prophet had properly imagined, with all the light of the world blotted out and trays of soda lime absorbing the carbon dioxide they breathed out, the two men had a unique view. "I felt like an infinitesimal atom floating in illimitable space," Beebe later wrote. "I was privileged to peer out and actually see the creatures which had evolved in the blackness of a blue midnight which, since the ocean was born, had known no following day." Beebe later fell out with Barton when the inventor used the bathysphere in a feature film of his own design, "Titans of the Deep", starring sharks and busty girls.

It was France who set man free underwater. During the second world war a French naval officer, Jacques Cousteau, invented scubaself-contained underwater breathing apparatus. In 1948, a Swiss scientist, Auguste Piccard, reluctantly sold his bathyscapheliterally, deep boatto the French navy. Piccard was the model for Professor Calculus in the Tintin comic books. He had worked with Einstein and touched the stratosphere in a pressurised capsule attached to a balloon. He used the same principles in his bathyscaphe: the abyss might be reached by weights and escaped by balloon. There were strange scenes in which a prototype was lowered below the waves off France. Piccard looked out of the view-hole, together with a French professor, as Cousteau's pioneering scuba divers circled outside. The professor was overcome. Hadn't he witnessed this before? Of course. As a boy, he had seen an engraving of the same scenethe captain, the professor, the divers outsidein Jules Verne's "20,000 Leagues Under the Sea".

In 1954, two French naval officers, George Houot and Pierre-Henri Willm, made the first dive to abyssal depths, sinking 4,023 metres in the FNRS-3 bathyscaphe, and breaking the surface in the tropical waters off Senegal. "Our craft is a blind, clumsy, limping creature, compared with what is to follow," said Houot. Yet the Senegal dive proved the starting point of manned ocean flightless celebrated than manned space flight, but no less heroic.

In many respects, the ocean is more hostile than space. Even with a futurist exoskeleton, the human body is too liquescent to contemplate stepping onto an ocean floor. There will never be a Neil Armstrong moment. Space flight is about weightlessness, speed, and the pressure inside the capsule against the airless void outside. Ocean descent is about weight, slowness, tonnes of sea water bearing down, and the discomfiting realisation that humans are alien to most of our own planet. Space offers a sighted journey towards infinity, the ocean a blind journey towards finitude.

When Auguste Piccard parted ways with the French navy, his son Jacques found private investors to build a more advanced bathyscaphe, named Trieste after its backers' home city. After tests in the Tyrrhenian Sea, the Piccards sold the Trieste to the American navy, which immediately saw advantage in sending the craft into the Challenger Deep. Auguste was too old for such a dive, so Jacques descended with Lieutenant Don Walsh, an American naval officer. The men took pictures, confirming that there was life on the abyssal floor, but incredibly the photos were mislabelled and lost in the naval archives.

Bertrand Piccard, grandson of Auguste and son of Jacques, hopes that one day the missing photographs will be recovered. Bertrand, who is following the family tradition of exploration by seeking to become the first person to fly around the world on solar flight, recalls attending a screening of the film "20,000 Leagues Under the Sea" with his father Jacques. "I was only seven, but I vividly remember looking up at Captain Nemo on the screen and then looking at my father next to me and thinking, I have my own Captain Nemo."

Verne's masterpiece remains the childhood inspiration for many oceanographers, but it is striking how hospitable a picture of the deep it painted. Nemo, an Indian embittered by the Sepoy mutiny, sails the Nautilus effortlessly into the abyssal depths. There is no eternal darkness. It might as well have been a fish bowl. "Let the reader imagine a forest in the Hartz mountains, with trees clinging on the slopes of the steep mountains, but completely immersed in water," is Verne's description of an underwater hike to sunken Atlantis.