Bad news for beachgoers: Jellyfish exist in every ocean on earth (some are as big as refrigerators), and all of them sting. This we learned from the National Science Foundation’s cheekily-titled report, “Jellyfish Gone Wild.” Fortunately, the vast majority of stings aren’t harmful—and some are barely noticeable. If you or your travel companion does feel the sting of a tentacle, Dr. Oz suggests two fast-relief remedies that can be found at a beach snack bar or in your bungalow’s kitchen. “When a jellyfish attacks, it implants thousands of tiny darts, called nematocysts, into your skin,” he writes in the May issue of O. “If you’re stung, fill a bucket with vinegar and soak the affected area for 15 to 30 minutes; the acetic acid in the vinegar stops the nematocysts from releasing more venom (if you don't have vinegar, Coca-Cola is a slightly less effective substitute by virtue of its phosphoric acid). Next, scrape the area with a credit card or knife edge to remove any clinging nematocysts.” Dr. Oz says that some people are allergic to jellyfish, so those experiencing hives or wheezing should seek emergency help ASAP.

Find more surprising first-aid fixes—for sunburns, bug bites, cuts, and prickly heat—here.