From aqualung to bathyscaph

Until our day, the oceans have always raised huge barriers to man's curiosity and understanding. Enormous distances and stormy weather made early navigation uncertain and perilous. For the diver the sea was a hostile environment which discouraged or limited his daring. And even the fisherman, who draws his food from the deep, is still compelled to grope blindly—the only hunter in the world who does not see or who does not know his quarry. Finally, the oceanographer still lowers his instruments more or less haphazardly, rather like an explorer setting out to discover a new continent with modern equipment, but with his eyes blindfolded. 

Seeing under water, in order to be better able to understand and interpret what we are doing, will be an obvious necessity tomorrow. Only yesterday, it was an impossibility; today, it represents a conquest which, while barely begun by self-contained divers, has just been completed with the historic descent of the bathyscaph Trieste. It is now possible for us to descend, to observe and to take action at any depth. 

From the surface to a depth of 40 metres, there are fifteen million cubic kilometres awaiting the self contained diver. This is the sea's most living layer—the one that washes the coasts, the one where nearly all the plant life of the oceans is produced by photosynthesis. Life here obeys the alternation of day and night, it follows the rhythm of the seasons. At sunset, hosts of animals rise from depths as far as 600 metres down to come close to the surface and feed on microscopic algae or wage silent combats. At dawn, all these intruders, fearing light for various reasons, disappear back into zones reached only by a dim glow. 

Most of the time, sea water is clear. In the open sea, it is not unusual to find underwater visibility of more than 60 metres. There, sight is a vital and perhaps a predominant sense. The diver, equipped with a mask, can enjoy sight on equal terms with the fish. He feels reassured and at ease; often, he even feels daring.

Crystal waters turn milky when the sea is in bloom 

The crystal of the ocean waters turns milky in the spring when the sea is in bloom. Along coasts battered by breakers and washed by tides, water is often rather clear. But near harbours and estuaries, countless particles in suspension diffuse the light and at times divers cannot even see a hand in front of them. In these troubled waters filled with alluvial material or small grains of sand, many micro-organisms die because of their vulnerability to such conditions. Certain algae and most corals cannot survive here. But fish sometimes teem in such waters, either because of fear or hunger. Their eyes are of no use in such "foggy" conditions but other senses take over: for example, there is the sense which enables them to interpret the slightest pressure wave and tells them all that is going on in the fog. 

In the "sunny layer," divers equipped with breathing apparatus can stay down for an average of twenty minutes and enjoy considerable security and freedom of movement. Diving to a depth of forty metres, is becoming so simple that it is no longer an affair for professionals alone. It is a great deal easier to teach diving to a geologist than to teach geology to a diver! 

Milne Edwards was the first man to dive with a helmet and make observations of interest to marine zoology. Later, Pierre Drach pioneered scientific research with freediving apparatus. Under his leadership, the divers of the Calypso methodically gathered harvests in the Red Sea in 1951. In Germany, Hans Hass inspired university men to become divers. In the United States, the Woods Hole Oceanographic Institution trained an underwater photography, and exploration team; at the Scripps Institute in California, young scientists dived to discover new species, geologists observed and filmed the phenomenon of cascading, measured the resistance of sediments on the spot and studied an underwater canyon. In the Mediterranean, underwater archeology was born. Applied to the hunt for oil, geological prospecting has made use of self-contained divers whether in the Persian Gulf or the Gulf of Mexico. Diving has rapidly become an indispensable tool for the scientific exploration of the sea; its use is already being extended to polar expeditions. 

Let us end with a comparison: on land, in our own element, it can be said that the volume of space actually inhabited is that of a layer going from the ground to the tops of the highest trees. That adds up to about four million cubic kilometres—hardly more than a quarter of that upper layer of the sea accessible to divers! 

Below 40 metres, light seems to come from all sides: there are no longer any shadows. When you look up to the surface, you can no longer make out the reassuring gleam of the sun. Self-contained divers breathing air begin to feel the first attacks of "depth drunkeness"—in other words, nitrogen poisoning—which threatens their safety by dulling their instinct for survival... pressure, shadows and cold underscore the hostility of the marine world to man. Around 300 metres, in the visible part of the spectrum, there is only a pale light, sufficient to make out objects a short distance away once your eyes have become accustomed to the darkness. Beyond that it is practically night.

The "twilight zone" of eighty million cubic kilometres includes all of those provinces of the sea known as the continental shelf. Often, it infringes upon the steep slopes of the talus. This extremely rich zone is still not very well known even though it is the most widely used area for deep-sea fishing. The continental shelf represents 8 % of the surface of the sea; that is, an area slightly smaller than Asia.

Self-contained diving apparatus has enabled us to enter the twilight layer: breathing air, Italian divers have managed to reach a depth of 120 metres for a few seconds. With a mixture of helium and oxygen, an Englishman has gone down to 165 metres. But these forays must be classed as isolated feats and a few seconds at such a depth must be paid for with hours of decompression under medical supervision. Between 40 and 300 metres, the explorer must protect himself with a rigid shell; either a sphere hanging from a cable or, even better, small free-moving submarines.

The French Office Française de Recherches Sousmarines (O.F.R.S.) and the research ship Calypso have just successfully put into service such a submarine at depths down to 300 metres. Its flattened shape has earned it the title of "diving saucer." The saucer only weighs three-and-a-half tons, it is easily stowed in the hold of a ship 40 metres long, and it accommodates two persons, a pilot and an observer. It can remain submerged more than twelve hours and it has enough electrical energy to run six hours under normal conditions. Its speed is modest (3 kilometres an hour) but adequate for exploration. It is propelled by hydrojets and the shape of its hull was designed for extreme maneuverability. It is equipped with a gyro-compass, sounding apparatus in three directions, a radio-telephone, a tape recorder, cameras to take still and motion-pictures, and a "hydraulic hand" to take samples.

Strange attacks of dizziness on the brink of a submarine gulf

Practically speaking, the saucer is the equivalent in the twilight layer to self-contained diving apparatus in the sunny layer. After sixteen test and training dives off the West Indies, the Cape Verde Islands and Corsica, the first saucer immediately began its scientific career. Professor Edgerton of the Massachusetts Institute of Technology and Professor Pérès of the Faculty of Aix-Marseilles in France went down to make observations, and scientists from many countries will follow in their wake beginning this summer. In the very near future, the twilight layer will be invaded by a number of submarines of the "'diving saucer" class.

When, aboard a diving saucer, you reach the edge of the continental shelf, you are struck by the abruptness with which the floor of the sea suddenly falls away. Under the bright gleam of your searchlights, the bottom disappears into the blue. You have to reason with yourself to fight off a feeling of dizziness. Then you put your bow down, on occasions as much as 30 or 35 degrees, to follow the slope downwards. Its surface is often scarred by underwater canyons, abrupt and extremely narrow, which sometimes have steps cut into their walls like giant staircases. Over such terrain, the best echo sounders in the world are unable to transcribe what you see through the portholes of a submarine designed for exploration.

But, at 300 metres, you must stop and turn the job to a craft which does not yet exist. However, the two bathyscaphs conceived by Professor Piccard—the F.N.R.S. III and the Italian "Trieste," (later acquired and transformed by the U.S. Navy)—are capable of descents to depths of 4,000 metres just as if they were lifts without any cables.

Twice, I was able to go down in a bathyscaph with Commandant Houot in the Toulon canyon. Sometimes broken up into tormented shapes, sometimes covered with mud, these "pre-continents" plunge sharply down toward the flat and uninteresting stretches of the seabed.

The great ocean basins, occasionally pierced by isolated rocky peaks, volcanoes or even mountain ranges, are mainly huge sedimentary plains. This zone, probably rather monotonous in appearance, is found at depths of between 3,500 and 6,000 metres. It alone accounts for 67 % of the total area of the seas and the oceans.

Earlier, I defined the boundaries of the "medium depths" as 300 and 4,000 metres. While the upper limit corresponds clearly to a physical and geological discontinuity, the lower limit, on the contrary, is dictated only by our present-day technical possibilities.

So far, the "medium depths'' have been penetrated about sixty times by the F.N.R.S. III and the "Trieste," two bathyscaphs based upon the principle of a large float filled with petrol to give buoyancy to a heavy steel nacelle. These heavy, delicate and not very mobile devices are the glorious pioneers of deep-water exploration. But their principle goes back to pre-war days, the construction was considerably delayed and, in fact, they were obsolete as soon as they were born.

Today, we can and we should be able to get along without any float at all down to a depth of 4,000 metres. Techniques of building hollow structures have made such progress that small submarines are to be built which will resist pressures of 400 atmospheres with an acceptable safety coefficient, but still with sufficient buoyancy.

The "Aluminaut" project in the United States is taking advantage of this technical progress by using light alloys. With three men on board and a full range of scientific apparatus, the "Aluminaut" will be able to cruise the sea several thousand metres down and will be small enough to be transported aboard a medium-sized oceanographic vessel.

In France, the O.F.R.S. is studying a project for an even more maneuverable submarine, in which extensive use is made of the most recent discoveries in plastics. This technical research has been made easier by the calculations of a safety coefficient which becomes lower and lower as operational pressures rises higher and higher (this is quite logical because relative changes in pressure caused by an accidental change in depth are smaller for a submarine designed to operate at 4,000 metres than for one built for 400 metres.

Until the "Aluminaut'' or similar devices go into service the bathyscaphs have opened new vistas in our knowledge of the "medium depths." The scientific balance sheet of the F.N.R.S. 3 is firmly on the credit side. Among the numerous observations made through its thick plexiglass portholes, two general conclusions have been brought out: in the open sea, the density of plankton certainly does not decrease regularly with an increase in depth (it is not at all rare to run through an extremely dense layer of plankton at 1,000 metres); and, secondly, the bottom of the sea, covered most of the time with thick layers of sediments, is the scene of intense underground life. There is hardly a square—yard without holes small, medium-sized or large—and these holes are dens whose inhabitants are still very much of a mystery to us.

The great ocean trenches (the Mariannas, the Philippines, Tonga, Porto Rico, etc.) are narrow furrows, located mainly in the Pacific. Their realm, properly speaking, can be said to begin at a depth of 6,000 metres and represents only 2 % of the total area of the sea. But they are critical spots on the earth's crust where it is either very thin or the scene of intense seismic activity. The systematic study of these deep trenches is of such great interest that "superbathyscaphs" are on drawing-boards or even under construction.

These superbathyscaphs will be large vessels with enormous floats containing petrol or other light substances, and having spherical hulls with room for a large amount of scientific apparatus. They will have enough power for a satisfactory range and cruising speed. The vast adjacent provinces between 4,000 and 6,000 metres, which the submarines of the "Aluminaut" type will be unable to probe, will be the hunting grounds of the superbathyscaphs.

The "Trieste," equipped with a special spherical nacelle, was able to descend into the bottom of the Marianna Trench, thus conquering the "Anti-Everest." It was a landmark in the history of oceanography, but though remarkable, this performance was really something of a special exploit. The "Trieste" is actually very poorly adapted to the path which it has opened to its successors, the superbathyscaphs.

Written by Jacques-Yves Cousteau and published in The Ocean’s secrets; new adventures in science, The UNESCO Courier, July-August 1960