Srowdfish became US last underwater test. Overall, during the years of testing US conducted 5 underwater
nuclear tests, including Swordfish.
Swordfish test pursued several objectives, including: Wepon effect on ships, submarines sonars, etc. For that several US navy vessels including 4 destroyers and a submarine on the surface wre positioned on various distances from ground(probably surface) zero, 2000 yd to 4500 yd; Evaluation of the safety for the vessels launching nuclear weapons; Proofing test of firing ASROC missile.
The missile was launched from the destroyer USS Agerholm (DD-826). Target surface zero) was approx. 4300 yd. away. Bombing was relatively precise, as the rocket missed its target by 20 yd. and exploded at a depth of 650ft 4o second after entering the water.
As usual underwater nuclear detonations are very spactacular. Swordfish was no exception. The resulting spray dome had 3000ft diameter and rose to 2100 ft in 16 seconds. Which means millions of tonns water in the air. Other than that the result was significant radiological contamination of the ocean.