Notice to all hands
It's the oldest rule on the water. Ask any captain, any guide, or the old-timer at the end of the dock. Nobody's sure where it started, and nobody's willing to test it.
Where it came from
Sailors have blamed bad luck on whatever was lying around for centuries. These are the four usual suspects.
Bananas spoil quickly, so ships hauling them from the tropics had to race to port. They ran hard and never stopped to fish. Boats that carried bananas were boats that weren't catching anything, and the fruit took the blame.
Big bunches of bananas made a good hiding place for spiders and snakes. A crew member bitten far from land was in serious trouble, and the bananas were what brought the danger aboard.
Ripening bananas give off a gas that speeds up the ripening of everything around them. A hold full of bananas could spoil the rest of a boat's food, and a crew without provisions is having a bad trip.
A wet deck, a rolling boat and a banana peel make a bad combination. Plenty of captains will tell you the rule exists because a slip on deck is no joke.
Today
On the water, people still follow it, or at least act like they do. Many charter captains and guides ask guests to leave bananas on shore, and plenty of anglers who say they don't believe it won't risk finding out.
The usual story is that the fish stop biting the day someone brings a banana aboard.
It costs nothing to leave the banana at home. And if the day goes badly, at least it wasn't your fault.
Before you board
Tap anything in your cooler. The captain will let you know.
Awaiting inspection
Strict boats count anything banana. When in doubt, ask the captain before you load the cooler.