The mauve stinger (Pelagia noctiluca) is a beautiful nocturnal hunter. They'll go deep, very deep, until nightfall. Then they'll move up to shallow waters to chase down plankton. The tentacles and bumps on the jelly will leave its prey with a powerful sting. They aren't the best of swimmers, but they seem to be spread easily by winds and currents, and so they are fairly ubiquitous. Odds are, if you've ever had a stinging encounter with a jelly, it just might be this one.

Relax. Enjoy. Repeat.

(The video, not the stinging.)