Quote Originally Posted by KnottedYet View Post
Whistling on a boat is actually a fairly practical superstition. If you are whistling on a boat, the crew might mistake your whistle for the bosun's whistled commands.

so whistling on a boat (big sailing ship type of boat) could lead to some hefty issues.
Actually, I was thinking of the superstition that whistling on a boat blows up a gale, and therefore washing/wetting your helmet would bring rain to your ride....