Radioactive sea spray caused extensive contamination.

The bomb was known as Helen of Bikini and was detonated 90 feet (27 m) underwater on July 25, 1946. It detonated 520 feet (158 m) above the target fleet and caused less than the expected amount of ship damage because it missed its aim point by 2,130 feet (649 m). The bomb was named Gilda after Rita Hayworth's character in the 1946 film Gilda, and was dropped from the B-29 Superfortress Dave's Dream of the 509th Bombardment Group on July 1, 1946. A fleet of 95 target ships was assembled in Bikini Lagoon and hit with two detonations of Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki, each with a yield of 23 kilotons of TNT (96 TJ). Blandy rather than by the Manhattan Project, which had developed nuclear weapons during World War II. They were conducted by Joint Army/Navy Task Force One, headed by Vice Admiral William H. The Crossroads tests were the first of many nuclear tests held in the Marshall Islands, and the first to be publicly announced beforehand and observed by an invited audience, including a large press corps. The purpose of the tests was to investigate the effect of nuclear weapons on warships.

They were the first nuclear weapon tests since Trinity in July 1945, and the first detonations of nuclear devices since the atomic bombing of Nagasaki on August 9, 1945. Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946.

Bikini atoll explosion