What happens when a nuclear bomb explodes under water

According to the cameramen who documented US atomic tests during the 1950s, the Wahoo and Umbrella underwater explosions were more amazing than a atmospheric nuclear explosion. Watch this stunning video and listen to him explaining his experience of living these explosions just 2.5 miles away.
more here: http://www.atomcentral.com/atomic-explosions.aspx#!prettyPhoto