I forgot to tie my drawstring before a high school swimming race. I dived in, lost my pants, momentarily stopped, decided (for some reason) to keep going, and came third.
After explaining to the official (an elderly lady) why I couldn't get out, I had to stand naked at the end of the pool until she got my towel, and then put it on while I was still in the water.
No "secret keel" jokes, please :P