The mini-submarine Nautile which is probing the wreck of the oil tanker Prestige off Spain's Atlantic coast is capable of operating at a depth of 6 kilometres (3.7 miles).
Equipped with an array of cameras and twin robotic arms, the Nautile usually dives with a crew of three to carry out underwater surveys and collect samples.
The crew have to work in a tiny 2.3 metre- wide cabin. It carries sufficient oxygen for five hours underwater.
The Nautile, owned by the French maritime research institute Ifremer, is best known for diving to the sunken liner Titanic.
The titanium-hulled vessel is fitted with a underwater telephone line and acoustic image mapping equipment, allowing it to relay footage of underwater objects to the surface.
Four separate thruster motors allow the Nautile to manoeuvre easily in any direction. It can travel at a speed of 1.7 knots.
On some missions the Nautile is fitted with a tiny robot probe, Robin. This can detach from the main submarine and operate by remote control, penetrating inaccessible or dangerous underwater wreckage.
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