The deck gun of the German submarine U-166, photographed by a NOAA remotely operated vehicle in 2001 at about 1,500 m in the Gulf of Mexico — the kind of deep survey that finds the wrecks ranked above. Image: NOAA Maritime Heritage Program.
These are the deepest wrecks ever located and surveyed, ranked by the depth of the wreck site. All five sank during the Second World War. The exact positions of some are deliberately unpublished, and the depths are survey figures that have been revised more than once as sonar has improved.
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USS Samuel B. Roberts (DE-413) — 6,865 m. A destroyer escort sunk on 25 October 1944 in the Battle off Samar, after attacking a Japanese heavy cruiser more than ten times her size. Victor Vescovo and sonar specialist Jeremie Morizet found her in the Philippine Sea on 22 June 2022; the first estimate of 6,895 m was revised to 6,865 m after calibration. Of the 224 crew, 89 were killed. The wreck is broken in two and lies deeper than any other ship ever found.
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USS Johnston (DD-557) — 6,468 m. A Fletcher-class destroyer sunk in the same action, after steaming into the Japanese fleet to cover the escort carriers. The wreck was discovered in 2019 by the research vessel Petrel and identified in 2021; the deepest part, an aft section, lies at 6,468.6 m in the Emden Deep. She held the record for the deepest wreck for less than a year.
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SS Rio Grande — 5,762 m. A German blockade runner carrying tin, copper and cobalt, sunk on 4 January 1944 by the cruisers Omaha and Jouett off Brazil. She was found in 1996, about 1,000 km offshore, and remained the deepest known wreck for 25 years. German blockade runners were fast, unarmed cargo ships; the Rio Grande was one of several caught in the South Atlantic that week.
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USS Indianapolis (CA-35) — about 5,500 m. A heavy cruiser torpedoed by the Japanese submarine I-58 on 30 July 1945, after delivering parts for the Hiroshima bomb to Tinian. Around 800 of her 1,195 crew survived the sinking; only 316 were rescued, after four days in the water, because her loss went unnoticed. The wreck was found in August 2017 by Paul Allen's research vessel Petrel, at about 5,500 m.
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SS City of Cairo — about 5,150 m. A British passenger steamer torpedoed by the German submarine U-68 on 6 November 1942, south of St Helena. Of 302 people aboard, 107 died. The wreck was located in 2011, and in 2013 a salvage team recovered about 100 tonnes of silver coins from her, the deepest commercial salvage ever attempted. She is a civilian casualty of the Battle of the Atlantic rather than a warship, which is why the site is not a protected war grave in the same sense.
Depth records keep moving because the tools keep improving: the same submersible that found the Johnston found the Samuel B. Roberts a year later, and both discoveries came from sonar that could resolve a hull at four miles down. Deeper wrecks are possible: the escort carrier Gambier Bay and the destroyer Hoel, both lost in the same battle, were still missing when the Roberts was found in 2022.