Originally Posted by
MarkCO
Apollo 13 had close to 4Kg of Plutonium that is now on the sea floor. Depending on depth, there is not enough oxygen to corrode even a cast iron casing. Sea water won't erode it either. Most casings for nuclear materiel are made of highly corrosion resistant materials anyway, so the risk of degradation to the casing is miniscule. Without maintenance, a nuclear device won't produce an atomic explosion after about 6 months.
Not going to say there is not a risk, but I think in the grand scheme of things, not that much of a risk.