Found on the web.There are many theories on why people believe bananas are bad luck for a boat. One superstition is that boats carrying bananas don't catch
fish. The origin of this belief dates back to the
Caribbean trade of the 1700s. The wooden
sailing boats of that time had to move quickly to deliver bananas before they spoiled, and fishermen had a hard time trolling for fish on such fast-moving boats, which is how the superstition came about. Another superstition that originated during that time is that bananas will cause a boat to sink. This belief developed after many boats never made it to their destinations, and all of the doomed boats were carrying bananas.
One of the creepier superstitions is that banana cargo could actually kill a man. In actuality, fermenting bananas do give off methane gas, which could conceivably get trapped below deck and kill any crew members unlucky enough to be working in the hold. Another popular theory was that venomous
spiders hitched rides in bananas, and once those bananas were onboard, the boat would be host to any number of lethal critters. And then, of course, there's the theory that banana peels cause crew members to slip and fall on deck [source:
Attah].