8. You've got sea lice.
South Floridians might not admit it, but most have had sea lice. The itchy, stinging creatures are actually microscopic larvae of thimble jellyfish found in the tropics. They like to get under swimsuits, causing "sea bather's eruption" -- but not the happy kind.
9. They feel no pain.
That's no reason to torture them, though. If they aren't bothering you, leave them to die on the beach, where they nourish the ecosystem.