A jellyfish is a type of creature known as a Coelenterata. That’s a fancy term to say it lives only in the ocean where the weight of the water can support it’s very delicate outer membranes or its “skin”. Jellyfish like to eat small marine creatures such as fish. If they couldn’t immobilize their prey, the fish could easily kill the jellyfish by thrashing around and ‘popping’ the jellyfish like you can on a beach.