In 1946, the United States conducted a series of nuclear weapon tests at Bikini Atoll in what is known as Operation Crossroads.
A total of two bombs were detonated to test the effects nuclear blasts had on naval warships. The second, named Baker, was the world’s first nuclear bomb to be detonated underwater.
During the first full second, the expanding bubble removed all the water within a 500-foot radius and lifted two million tons of spray and seabed sand into the air. As the bubble rose at 2,500 feet per second, it stretched the spray dome into a hollow cylinder or chimney of spray called the “column,” 6,000 feet tall, 2,000 feet wide, and with walls 300 feet thick.
Source: Rediff News