Set yourself straight once and for all when it comes to these seaside old wives' tales:

Myth: You have to wait an hour after eating to swim.

Yes, your stomach might protest (cramps, nausea) if you hit the water right after eating a really big lunch, but a full belly won't up drowning risk. In fact, if you're swimming laps, a small 100-calorie bite 10 minutes beforehand will actually help fuel your workout.

Urinating on a jellyfish sting eases the pain.

Truth: Pee won't help. Instead, pack vinegar: It deactivates the venom, says Mark Schick, collection manager at Chicago's Shedd Aquarium. As you pour, scrape off barbs with the edge of a credit card. Some stings are deadly; if you feel nauseated, head to the hospital.

Myth: Washing a cut in ocean water will speed healing.

Although clean salt water can kill many types of germs, the sea hosts a wide variety of bacteria--a very small number of which could cause infection if they were to get into an open wound. For that reason, you're better off rinsing a cut in clean tap or bottled water instead.