The bilge meter on a ship shows how much bilge water is currently in the ship. It is visible on the Vessel panel.
The bilge meter is constantly increasing—even the simple act of sailing around lets water into the bilge—and lots of bilge water keeps a ship from going as fast as it could otherwise. Movement tokens are also produced more slowly in a sea battle when the bilge level is high. The amount of bilge water decreases when pirates perform the bilging puzzle, but damage increases the rate at which the bilge meter fills up.