I think we also have to be weary of all the diving that may have happened (RE: the diving pic) and their use of the water with this. Perhaps the amount of explosives under sea vessels is underestimated along with what may be inside.
I mean do ships' underbellies get scanned everytime they dock? Hardly!
just a thought yknow..
I think that it is possible for a scuba diver to attach explosives to the hulls of ships, underwater.
Using magnets or with wire.
Or have I read too many good books over the years?