Much of those superstitions is actually based on sailing risks, luck, and omens and portents that are given associative meaning.
Sailors have lots of superstitions that are specific to being a mariner. Do you know of any of those superstitions?
The number of 7 is a really interesting number. Sounds interesting, do you know of the interesting number paradox? It's a sort of paradox which happens when natural numbers are classified as dull or interesting. No but I know people have superstitions of numbers, where did that even begin with?
The origins of many of these superstitions are based in the inherent risks of sailing, and luck, either good or bad, as well as portents and omens that would be given associative meaning in relation to the life of a mariner, sailor, fisherman or a crew in general.