The lifeguard told the mother to make her young son stop urinating in the pool.
"Everyone knows," - the mother lectured him, "that from time to time, young children will urinate in a pool."
"Oh really?" said the lifeguard, "from the diving board!?!?"
Snails produce a colorless, sticky discharge that forms a protective carpet under them as they travel along. The discharge is so effective that they can crawl along the edge of a razor without cutting themselves.