Today, I took a break from my work and walked along the beach. I don't spend a lot of time on the beach during the day but it was quite windy and the ocean was rough so I pretty much had the beach to myself. Soon, I saw another reason why the beach was deserted. The shoreline was littered with seaweed and little blue balloon-like objects. Growing up on Fort Lauderdale beach, I knew these were Portuguese Man o' War. My parents had warned me about them as early as I can remember. Every year I hear about some unfortunate tourist who touched one in the ocean, stepped on one that washed ashore, or even tried to pick one up, not knowing what it was!
Contrary to popular belief, the Man o' War is not a jellyfish. It is a specialized siphonophore. Its blue "balloon" is an air bladder which it inflates to float on the surface of the ocean. Long, venom filled tentacles dangle beneath the surface, paralyzing fish that come in contact with them. The following is from the Wikipedia article:
Detached tentacles and dead specimens (including those which wash up on shore) can sting just as painfully as the live creature in the water, and may remain potent for hours or even days after the death of the creature or the detachment of the tentacle.
Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin which normally last about forty-five minutes after which it should subside. However, the venom can travel to the lymph nodes and may cause, depending on the amount of venom, more intense pain. A sting may lead to an allergic reaction. There can also be serious effects, including fever, shock, and interference with heart and lung action. There have even been deaths, although this is rare. Medical attention may be necessary, especially where pain is intense or there is an extreme reaction.