The best joke I heard of is for wet suit diving only,... but someone put red food dye in one of the boots of my instructor & green in the other. He put the red boot on first & had to take it off, when he saw the dye, he though he'd sliced a vein open or something. Scared him a bit for a minute, but then he's a big wussie about blood & stuff. By then, his foot was already dyed red, He didn't think about it, but a few minutes later put the green boot on. When he took them off, he had 1 green foot & 1 red foot for 2-3 days until the color wore off. Harmless, but embarrassing.
Left foot should be red; right foot green. Gotta keep it nautical!