2 November 2011
Last updated at 09:36
Wednesday is the 10th anniversary of the adoption of the Unesco Convention on the Protection of Underwater Cultural Heritage, which is designed to protect shipwrecks. The Truk Lagoon, in the Pacific, is home to the wrecks of 60 Japanese ships and 275 planes.
Every day thousands of ships traverse the world carrying cargo or passengers. Some do not reach their destination. In 2004 the MV Selendang Ayu, a Malaysian ship carrying soybeans from Seattle to China, foundered and broke apart off the coast of Alaska. The two parts of the ship floated separately before sinking.
Wrecks are being discovered and explored all the time. Only last week an American team, led by Pat Croce, claimed to have found the remains of two ships belonging to legendary English seafarer Sir Francis Drake, off the coast of Panama.
Under the 1986 Military Remains Act, the wrecks of a number of British warships around the world are protected and any British citizens trespassing on them can be prosecuted. One of these is the destroyer HMS Sheffield, which was sunk by the Argentinian navy during the 1982 Falklands conflict.
Sean Fisher, whose grandfather Mel found the Spanish treasure ship Nuestra Senora de Atocha, poses with some of the gold found on the wreck, off the Florida Keys. Mr Fisher says he is proud to call himself a "treasure hunter".
In 2004 Hector Bado oversaw the raising of the rangefinder from the German battleship Graf Spee, which was scuttled by its captain just off the coast of Uruguay in December 1939. The Graf Spee had been damaged during the Battle of the River Plate and was cornered by the Royal Navy in Montevideo.
Some ships are grounded but manage to refloat and finish their voyage. The Liberian-flagged container ship Rena struck a reef off the coast of New Zealand earlier this month. She had been leaking oil for weeks.
Many ships come to grief on the shoreline and take years to break apart. This tugboat, abandoned after grounding at Vila Nova de Milfontes, on the coast south of Lisbon, Portugal, provides a dramatic image.