Any of various floating, warm-water marine Physalia , class Hydrozoa) found worldwide but mostly in the Gulf Stream and the Indian and Pacific oceans.
The medusa -form body consists of a translucent, jellylike, gas-filled float, which may be 3–12 in. (9–30 cm) long. {{link=polyp">Polyps beneath the float bear hanging tentacles up to 165 ft (50 m) long. Nematocysts on some polyps paralyze fish and other prey. Other polyps then attach to, spread over, and digest the victim. A third type of polyp is involved in reproduction. The painful sting of Physalia can cause fever, shock, or disruption of heart and lung function.