Oh no, the urine myth is making a re-appearance. I posted this previously on the forum, maybe it's time for refresher:
As a person who has had considerable training and internship in Poison Control Centers, I can tell you that there are no conclusive research studies that have proved that urine or ammonia has any value whatsoever in relieving jellyfish stings. If fact, depending on the urine, it can actually make it worse. Urine contains so much fresh water, it will actually make any remaining nematocysts ( which contain the toxin that causes the discomfort) to fire, releasing more toxin. That's why we recommend using seawater only to rinse the area. Vinegar is 5% acetic acid,(CH3COOH) which has shown to neutralize unfired nematocysts so that they cannot further inject venom. Now, keep in mind, this is true for jellyfish stings, not the Portuguese Man-O-War, a jellyfish look-a-like, but different creature. Some of our studies have shown vinegar to cause their nematocysts to release venom. That is why I recommend the baking soda/seawater paste instead. There is a product you may want to want to have with you called Jellyfish Squish spray. I keep a couple bottles in my casa just in case. It's good to use after the treatments above to help the pain and discomfort.