|H-912 transport container for Mk-54 SADM|
The two-man team would place the weapon package in the target location, set the timer, and swim out into the ocean where they would be retrieved by a submarine or other high-speed water craft. The parachute jumps and the retrieval procedures were practiced extensively.
In the 1950s and 1960s, the United States developed several different types of lightweight nuclear devices. The main one was the Mk-54, a cylinder 40 by 60 centimetes that weighed 68 kilograms. It was fired by a mechanical timer and had a variable yield from 10 tons up to one kiloton. 300 SADMs were assembled and remained in the US arsenal until 1989.