If you get stung, remove any clinging tentacles with your fingers, or by scraping the skin with a credit card. Don't use remedies such as hot sand, kerosene, or urine, and don't douse the sting with fresh water it forces toxins further into the skin. Dilute vinegar is good first aid for box jellyfish and Portuguese man-of-war stings. Ice is best for the rest.
Further information from Ken Landow, MD