A 14 Ton atomic bomb in WW_II??

Hi! All
Subject could sound odd, but if any of you would have seen a tv documentary I saw a few years back, you'd be as surprised as I was. Documentary I saw was about a sci independet team investiganting somewhere in Pacific deeps (I do not remember the point) by means of a sub-bot. Bot sunk a few miles deep and during one immersion the bot filmed what after some research was a WW_II cargo vessel; then after more research it resulted to be part of a secret convoy sailing out normal routes and finally after sending the bot through a big hole (japanese torpedo) in hull, it measured high radiation, also no life (there is not too much so deep, anyway) some hundreds feets around and finally they filmed what it looked to be a huge, large bomb. This is the last point for me to ask you, please, because I've read a lot about WW_II, secret projects and weapons but I missed THIS. These people, the sci ocean investigators, discovered a top secret project which consisted in launching this bomb just in top of Fujiyama volcano. I'm completely lost about this point. Never heard something like this and, since I have no more info, if this was true, I presume some of you could post some links on the subject.
Thx in advance & I apologize for this length.
disinher