Well, this was an eye-opener. I never thought very much about AC vs. DC in ships. Here is my three cents worth:

1) Given that path of electricity in a ship is fairly short, it would seem power losses are not that significant in DC.

2) Keeping the the three AC phases in concert with each other might be more difficult when the ship takes a hit.

3) DC is more repairable than AC.

My experience in the oilpatch is that most remote transmission is AC, with the generator less than 100 meters from where the electricity is being used. But then again, oil drilling rigs are not being shot at.