The cannons are what do the damage to other ships. They are low-power BB guns that can pierce the thin armour of another ship. They can fire as often as you can press the button (semi-auto). There is a limited number of rounds, though, and once you're out, you're out.
The bilge pump takes the water in your hull and spits it out. This is handy when there are holes from other ships in your balsa siding. Without this device, even one hole can prove fatal. The pump can only keep so much water out; too much damage and you're going under. All things considered, the pump is your true armour in this game.
