What do I know? I am not fond of water and sharks scare me. But if a Somali pirate were to come upon my 50,000 ton container ship.. I would probabally say "Do one" then lob house bricks down on their Dhow. Those ships are the hight of a small Council block. Whats the problem? You could shit on the bastards and spoil their day. House bricks. Piled on the deck. It's not a naval solution, but it'll give them pause for thought.