Portuguese man o' war

Physalia physalis

Family Physaliidae - hydroids

Colony of 4 types of polyps: 1) the air bladder is translucent, balloon-like, one end wider than the other; back with raised, compressed air canals (sail); colors range from blue, purple, pink, to green; stays on surface of water, acts as a sail; 2) long, string-like tentacles under air bladder, dark green or purple, covered with stinging cells; 3&4) digestive and reproductive polyps form clusters of short, stringy masses that dangle beneath the air bladder, colors the same as tentacles.
Similar Species
Another Physalia, P. utriculus, lives in the Pacific Ocean. It is distinguished from P. physalia by having a shorter float (6 in) and only 1 long stinging tentacle.
Gulf, ocean surface
Maximum Size
float up to 30 cm (12 in), tentacles up to 50 m (164 ft), typically 10 m (33 ft)
Other Common Names
Previous Scientific Names
Not a true jellyfish. Venomous. Stinging cells can cause very painful welts. Fatalities have been reported due to the Portuguese man o' war.