What first aid would you use if a person was stung by a jellyfish?

First, do not touch the jelly that is on the person.

Second, try to wash off the jelly with something.

Pull out any spines that you can find with your fingernails.

If you have a base like dilute liquid ammonia or baking soda, apply it so that it can neutralize the acid in the jelly.

Watch for shock, and if the stung area is more than several square inches, transport the victim to a hospital for treatment of the stung areas.

Oddly, the creature that is most harmful is the Man o' War "jelly fish", which is not even a jellyfish!