Once, when I was about 12, my dad told me to tie up our boat to the dock and I grabbed the end of the rope on this 15 footer and put a big-old granny knot in it around the corner of the post on the dock; my dad grabbed some boxes and a cooler and stepped into the boat, or should I say stepped onto the boat, which then proceeded to display the heretofore hidden length of the line.
By the time I got done laughing he was too tired to chase me any longer.