If it were safe from retrieval I am pretty sure they would let someone know. Certainly other governments would be interested in insuring there was no leakage. B

If it were safe from retrieval I am pretty sure they would let someone know. Certainly other governments would be interested in insuring there was no leakage. Both the US and Russia have lost nuclear submarines and those are well known and even checked for issues by nearby nations. Now during the 50s and 60s all bets are off, but I doubt any weapon declared one way or another fully escaped attention for this long. You want a real scare, go read up on Operation CHASE which where they were dumping even chemical weapons into the sea