Long Long John

Odyssey was founded in 1994 and specialises in recovering treasure lost at sea. In May, it announced that it had discovered an unnamed shipwreck in the Atlantic and recovered 500,000 coins of Spanish origin. Based on initial samples, these might be worth $500m. The company has not revealed the name of the wreck or its location but speculation has centred on Merchant Royal, an English ship laden with Mexican loot that went down in 1641, and Nuestra Senora de las Mercedes, a Spanish warship sunk by the British in 1804.

Finders are not always keepers on the high seas, though. Odyssey has filed a claim to the coins in a US court, but Spain may be entitled to some of the treasure if the wreck turns out to be in its waters (which Odyssey denies), or is a sovereign warship (which is unclear). Still, this appears to be factored into the $331m enterprise value, which discounts about a 30 per cent risk of an unfavourable legal decision.

Odyssey already has pragmatic agreements with the UK and Spain regarding another potential wreck. Finally, while competitors, such as the UK's SubSea Resources, have yet to strike it lucky, Odyssey has a track record. In 2003 it recovered $75m in coins from the 1864 wreck of SS Republic. There are an estimated 3m shipwrecks worldwide - that could be a lot of pieces of eight.