That explosion was part of the "Top-Secret" directive, that if discovered, they cache would self-destruct...
Heavy seas took its toll... but seriously, the life boat and its cargo were most likely "damaged" by the high seas, and at a certain "level" of destruction, "POOM!!!" goes the boat... Wait until it happens next to your submarine, and you take damage from it!... not cool! That's why I always try to be in slow reverse with a starboard rudder, so that the submarine goes away from the raft...
