The jellyfish have deadly tenticals. The venom in the cells are called cnidocytes. It is held in harpoons which are located in the cell. When the jellyfish touches you it shoots out its venom faster then we blink and poisons the body part it touches with its tentacles.
If being stung by a box jellyfish, some symptoms would be burning, prickling, stinging pain, and etc. After getting stung it leaves a purple or brown mark on body. It could cause death if being stung.
When going diving always wear a stinger suit, to protect you from being stung. Look for signs to if there are any jellyfish warnings at the beach. Avoid the waters during jellyfish season which is In August.
First remove the stingers. Then remove any pieces of jellyfish tentacle in your skin by rinsing the wound with seawater. Then rinse with vinegar or apply a baking soda paste. Take a hot shower or apply ice packs. Finally take a pain reliever and put on lotions.
Always take the stinger out, if not then it could get infected. Vinegar is more effective then peeing on your self. Put ice on the sting because the sting burns and the ice will cool the burn down.