Those are not supertitions of modern sailors, some of those are not believed in anymore.
Sailors believed that sharks know when someone is going to die. They thought that she will follow the ship if something bad is about to happen.
Sailor would never shoot sea-gull. They believed that sea-gull carried soul of dead sailor.
It's bad luck to start sailing (that is, to leave the harbor) on the friday, because it's believed that Jesus had been crucified on friday.
Man of the Sea rarely knew how to swim. They believed that, if sea could have a taste of them, it would chase them down until it finds and kills them.
