US$50m coin Atlantic salvage

SS City of Cairo carried some 236 people and 100 tonnes of silver coins belonging to the UK Treasury when it sank in 1942. It was sailing from Mumbai to Britain via Cape Town and Recife in Brazil when it was spotted by a German U-boat and hit by two torpedoes.

DOS found the wreck after almost four years of searching, proving to be a challenging search with water depth exceeding 5,000m and the presumed site some 1,000 miles from the nearest land in the foothills of the mid-Atlantic ridge.

Research revealed “usual contradictions” between the positions given by the submarine and that from the ship’s officers. For DOS, the seafloor also played its part in ensuring it was a challenge, with ridges and canyons throughout the area.

SS City of Cairo was found broken in two and buried deep in the seafloor silt. Under contract with the UK Ministry of Transport, DOS recovered several tend of tonnes of silver coins from a depth of 5,150m – a world record depth.

With the world record depth came difficulties for the salvage crew. The combination of pressure, temperature, repeated dives at this depth and other issues resulted in multiple breakdowns of systems DOS hadn’t experienced before when working in 3,000-4,000m depths.

DOS left a plaque recording its finding and visit before the team finally left the site back in September 2013.

By Rachael Doyle