Among the organisms whose presence often prompts these types of warnings are jellyfish , probably the most common on many coastlines. Their tentacles have stinging cells that can cause discomfort upon contact with the skin. Depending on the species and individual sensitivity, the consequences can range from mild irritation to reactions requiring medical evaluation. Therefore, it is always advisable to avoid approaching these animals , even when they appear motionless on the sand.
Another species that often prompts the raising of the purple flag is the stingray . These animals tend to remain partially buried in shallow sandy bottoms, where they go unnoticed by those walking in the water . They generally pose no risk if left undisturbed, but accidental contact can cause a painful injury. To minimize this possibility, specialists and lifeguards often recommend shuffling your feet on the sand, a technique popularly known as the “stingray walk ,” which alerts the animal to move away before someone steps on it.
There are also lesser-known organisms, such as so-called sea lice , which are actually microscopic larvae of certain marine animals. These can become trapped between the skin and a swimsuit, causing irritation and itching hours after leaving the water. Although they generally don’t pose a serious problem, they can cause significant discomfort.
In some regions , Portuguese man-of-war specimens can also be found , an organism often mistaken for a jellyfish, although it belongs to a different biological structure. Its long tentacles can retain their stinging ability even after the animal reaches the shore. For this reason, it is never recommended to touch these specimens, even if they appear dry or lifeless
