Crossroads consisted of two detonations, each with a yield of 23 kt. Able was detonated over Bikini on July 1, 1946 and exploded at an altitude of 520 ft but was dropped by aircraft about 1,500 to 2,000 ft off target. It sank only five of the ships in the lagoon. The second, Baker, was detonated underwater at a depth of 90 ft on July 25, sinking eight ships. The second, underwater blast created a large condensation cloud and contaminated the ships with more radioactive water than was expected. Many of the surviving ships were too contaminated to be used again for testing and were sunk. The air-borne nuclear detonation raised the surface seawater temperature by 55,000 °C (99,000 °F), created blast waves with speeds of up to 8 m/s, and shock and surface waves up to 98 ft high. Blast columns reached the floor of the lagoon which is approximately 230 ft deep. The Bikini Island King visited Bikini Atoll in July after the second atomic bomb test code-named Baker and found it apparently in good condition.

A third burst, Charlie, planned for 1947, was canceled primarily because of the United States Navy's inability to decontaminate the target ships after the Baker test. Charlie was rescheduled as Operation Wigwam, a deep water shot conducted in 1955 off the California coast.

To conduct the tests, the United States assembled a support fleet of more than 242 ships that provided quarters, experimental stations, and workshops for more than 42,000 personnel. The islands were primarily used as recreation and instrumentation sites. To support the nuclear bomb testing program, Seabees built bunkers, floating dry docks, steel towers for cameras and recording instruments, and other facilities on the island to support the servicemen.

Information link

https://en.wikipedia.org/wiki/Nuclear_testing_at_Bikini_Atoll