One of the things I learned when I was writing a folklore column in Messing About in Boats is that no matter how you try to lie, sooner or later, even great improbablities will reveal themselves to you as truth.

Many years ago, when I was down in the Amazon, I was told never to relieve myself over the side of the boat. There are very small, very hungry fish there who will swim rapidly up your urine stream into you and make themselves at home in your bladder. As I considered this too improbable to be true, I ignored the advice and ended up at the doctor's having that son of a fish cut out of me. Both the problem and the cure were very painful.