Manned exploration of the deep

A thousand leagues under the sea...

The first recorded use of a submarine took place in the River Thames. A Dutchman, Cornelius van Drebel, succeeded in taking his machine to a depth of 4.6m! Not a huge depth, but it was a start.

In order to explore really deep waters, a sphere is the best shape to withstand the enormous pressure of water. As you go down through the water the pressure increases by one atmosphere every 10 metres. An ‘atmosphere’ is the pressure equivalent to air pressure at sea level, about the equivalent of loading one kilogramme onto one square centimetre. So, at 10 m depth the pressure is doubled to become 2 kilos per square centimetre, at 20m trebled and so on.

In 1934 the first bathysphere [bathy=deep, sphere = ball] was tied by two Americans; Beebe and Barton. This successfully reached 1000m metres. In 1948 a Swiss gentleman improved the design and built a bathyscaph (bathy=deep, scaph=ship) which he took down to 1400m. This later was developed into the Trieste (pictured left), a famous deep water exploration vessel. The Trieste started its life by reaching 3139m but after modifications was, in 1960, used to explore the Marianas trench to a depth of 10,915m.

A more recent submersible, capable of holding three people, is ALVIN (left). This vessel can reach 4000m and was used by Dr Ballard in 1985 to discover and explore the wreck of the Titanic (right), which sunk 75 years earlier. In 1966 ALVIN was used to find a ‘lost’ hydrogen bomb!


It has been a long dream of many to be able to swim and explore underwater. Unfortunatley, due to the increase in water pressure, the human lungs cannot expand against the external pressure much below 0.45m – 45cm. The solution is to supply piped air which is pumped to equal the water pressure. This has to be supplied through reinforced tubes which would otherwise collapse and cause the diver to suffocate.

In 1943 two Frenchmen, Jacques Cousteau and Emile Gagnan, designed and built the first aqualung which enabled divers to be free of cumbersome tubes and safety ropes. SCUBA [Self Contained Underwater Breathing Apparatus] diving was born. The clever design uses air which is stored under pressure in a cylinder worn on the back. This, and various valves, allow the air about to breathed in, to reach a pressure equal to the external pressure.

Diving may not contribute greatly to exploring the very deep waters but, the skills of divers are required to set up and maintain some of the data gathering activities. Today’s divers can go well beyond Van Drebels first submarine dive!

It's not all plain sailing...

Although manned exploration sounds like fun, it is very expensive and potentially dangerous. A lot of extra care and cost is incurred through sending people down to the deeps. The latest trends have been to use remote controlled systems, including robots, cameras and various sensors which can gather huge amounts of various data much more quickly.

Find out more about ocean exploration:

Ocean exploration: Part 1
Ocean exploration: Part 2
Manned exploration of the deep
The Challenger Expedition
Ocean exploration timeline
Navigation: Dead reckoning
Early navigation
Improved navigation
Modern navigation
Mapping the seafloor
Exploring below the seabed

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February 2007