I then asked them "What do pirates ride the waves with?" and they all answered Ships. "And what do pirates do when they meet other pirate ships?" Fight them. We headed down to the basement where they found two pirate ships. (Two large appliance boxes painted and cut so that one of the corners was the bow of the ship, complete with mast and flag). In each ship they found a bucket of cannonballs (balled up newspaper held together with masking tape) I had them number off 1, 2 and all number 1's were in one ship and number 2's in the other, each ship captained by a birthday boy. The teams were Ryland's Rogues or Luke's Liberators, named after the birthday boys.   The game was called "Sink the Enemy" and the idea was that when they heard the whistle they had to throw as many cannonballs as they could into the other ship. When the whistle blew again all action stopped. Cannonballs were counted and whichever ship was sunk (most cannonballs in the ship) that team had to walk the plank. Walk the Plank was a board set up on crates with toy sharks, crocodiles, whales, fish, etc. scattered underneath. Of course all the kids wanted to Walk the Plank so we had to play Sink the Enemy 3 or 4 times! (We started adding variations to make Walk the Plank harder eg. Walk backwards, hop on one foot, jump over obstacles, etc.)