Portuguese man o' war

The Portuguese man o' war looks like a jellyfish but is a siphonophore: a colony of specialized, genetically identical individuals working as one animal. The blue, violet or pink balloon on top rides up to six inches above the waterline, while the tentacles below average about 30 feet. The sting is rarely deadly but very painful, and it leaves welts. Two things matter on the beach. A stranded float can still sting weeks after washing up, so leave the pretty blue balloons alone. And vinegar, the remedy for box jellyfish, can make this sting worse; hot water is the better relief.