At some point you are bound to encounter the Portuguese man-of-war (Physalia physalis) on Treasure Coast Beaches. Though they are found in every ocean except the Arctic, they tend to wash up on Florida beaches in greater numbers with strong spring winds. And though they don't really have and official "season" it's not unusual to start spotting them on our shores at this time of year.
This fascinating creature is not a jellyfish at all but rather a siphonophore- a colony of animals comprised of specialized organisms known as zooids. Zooids cannot survive on their own, so they merge into a tentacle structure, each one serving a different communal purpose such as catching prey, digestion, reproduction, and facilitating travel. These tentacle "colonies" grow to an average of 30 feet but can extend as much as 165 feet. Despite their diverse functionality, zooids are genetically identical, like clones. The top of the man-of-war structure is called a pneumatophore, or a "float." This is the brightly colored blue-purple bladder that is so recognizable. This "float" is filled with gasses including carbon monoxide and acts as a sail.
The man-of-war tentacle can remain venomous once the colony has died. Even a severed tentacle can still sting. For humans, a sting can be extremely painful, but rarely deadly. In any case, curious beachcombers and well-intentioned folks who participate in beach clean-up should be cautious. Because of their color, they can easily be misidentified as trash or plastic. When their concentration in our waters gets high enough, lifeguards will typically fly the purple flag indicating hazardous marine life. It’s a good idea to avoid swimming during these times. They're nearly impossible to see in the water and can ruin a perfectly good beach day!
If you do get stung, don’t panic. Researchers have found that a man-of-war sting doesn’t differ from any other jellyfish sting and can be treated the same way, except for rare allergic reactions which can happen with any venomous creature. Those findings are published in the MDPI Journal of Toxins. The recommended treatment is a white vinegar rinse to neutralize toxins on the surface of the skin, removal of any remaining tentacles using a tweezer, followed by a hot pack to neutralize any venom beneath the skin. This is also how most lifeguards in Florida treat man-of-war and jellyfish stings.
Of course, if you experience any signs of an allergic reaction such as difficulty breathing, swelling of the throat or tongue, or excruciating pain that does not go away within hours after treatment, you should seek medical attention right away.