We've been told for decades the best way to treat a jellyfish sting is to have somebody pee on the site, which will somehow stop the pain and help counteract the jellyfish venom.
This myth has given "helpful" people license to urinate on the unfortunate souls who tangled with a jellyfish, and yet it's fairly common knowledge that urine doesn't do much more than stink up a jellyfish sting.
..the amount of acid you’re looking for just isn’t in urine. While your pee IS acidic, usually with a pH of around 6, it isn’t acidic enough to denature porins and prevent them from hole-punching your cells. And the same goes for rinsing with fresh water. …Your best bet is to find a safe, jelly-free area in the same body of water where you were stung and rinse the affected area with salt water.
-Via Laughing Squid