This footage is from operation Hardtack and this explosion is from an 8-kiloton nuclear bomb named Umbrella.
That’s insane. But what’s even more insane is that that huge explosion was only 8 kilotons. In comparison, the bomb dropped on Hiroshima was 16 kilotons (double).
Maybe a few hundred yards. For scale, the ship is over 400 feet long, and the water column reached a height of over a mile.
Here is a picture where you can see all of the water splash!