The divers were detained on 1 May while working on a sunken ship 18 nautical miles off the disputed Abu Musa island.

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Also known as the Marine Silk Road Museum, this institution contains a sunken ship more than 800 years old in an aquarium like setting.

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Iron-eating microbes are steadily breaking down the actual sunken ship, but the pieces already culled from the wreck's 13-mile debris field are "spectacular, " said John Joslyn, the owner of a pair of Titanic theme museums in Missouri and Tennessee who helped to fund the first salvaging expedition in 1987.

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The true nature of the sunstone will probably not be settled until and unless one turns up in either a sunken Viking vessel or a ship burial.

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