There are a lot of superstitions on board a ship ... and I guess they all come from times when safety at sea was not as good as nowadays and seamen really were risking their life.
First of all, and maybe the most well-known, is bringing a woman on board a ship brings you bad luck (which is obviously totally unfair). In fact women onboard a ship were supposed to distract the crew and place it in peril.
I have selected a few more (among hundreds):
- You are not supposed to say the word ‘Rabbit’ ... it is a word that brings bad luck.
- Throwing stones overboard is bad luck (because it causes ripples, which causes waves and brings storms).
- Having flowers on board is bad luck as well because flowers are used for funerals.
- Losing a hat overboard signified a long trip.
- Black travel bags are considered bad luck as well. For some reason.
- Don’t whistle as this would cause a storm at sea. (We say ‘whistling up the wind’ and it also may come from the times when ships were using steam .. a leak in high pressure will make a whistle).
- Ship’s bell should never ring itself. It is an omen of death.
- You shouldn’t leave port on a Friday. (Because Christ was crucified on a Friday.)
- In old times, drinking wine on the deck was considered to bring you bad luck because it is an insult to the gods.
- Killing an albatross or a seabird is supposed to bring you bad luck because they are thought to carry the souls of dead sailors.
- A naked woman is supposed to calm the sea (that is why most of the time figureheads are naked women).