Hey atleast we don't have swarms of deadly jelly's like they have near OZ, the little itty bitty ones are worse than the Box!
Once you get stung it's gonna hurt... vinegar, ammonia, meat tenderizer, etc. only gets rid of the stinging cells that are on the skin. The trick is to NOT rub the affected area, rinse it off in salt water or vinegar... fresh water makes the stinging cells mad. Only rinse with fresh water after you've gotten rid of the stingin cells on the skin.
For pain... any topical cream with anti-itch or anti-histimine funtion, benydryl for severe (local skin) reactions.
FYI: jelly fish have the same type of toxin as BEES! Any small children or elderly, as well as those with known allergic reactions to bee stings should be watched closely... for signs of breathing problems.
Good news... material as thin as pantyhose can keep you protected from the sting. If you don't want to wear a wetsuit then buy a skin or rashguard!