What is a good luck charm on a ship?

I'm not sure about specific charms, but there are lots of things that are considered good luck. A nautical star brings a sailor good luck (I'm not suggesting you go out and get a tattoo!). A black cat aboard a boat is supposed to bring good luck. A naked lady is supposed to calm the seas (which is why there are naked ladies on the bows of old sailing ships). There are lots of old sailing superstitions...but one almost universal bad luck one is having a banana aboard...a real no-no among fishermen.