jelly fish

If you happen to have some vinegar on hand that could work - (unless its a porteguese man o war) be careful if the jelly fish is still attached! Vinegar by the way has many many uses - not just for cooking. Don't use fresh water to clean wounds as the change in ph can release more venom. If you have nothing - you could use urine - you'd be suprized how many things this is good for - even feces has been used for first aid - not of jelly fish though - and spiderwebs.