The “Baker” nuclear experiment, part of Operation Crossroads, at Bikini Atoll in the Marshall Islands, on July 25, 1946. The 40 kiloton atomic bomb was detonated by the U.S. at a depth of 27 meters below the ocean surface, 3.5 miles from the atoll. The purpose of the tests was to study the effects of nuclear explosions on ships. 73 ships were gathered to the spot — both obsolete American and captured ships, including the Japanese battleship “Nagato”. You can clearly see the various ship types on the picture.