Something happened today. I was on a beach with my kids, and suddenly all the lifeguards came down to the water, put up the purple flag, and asked everyone not to come close to the water. Why? They sounded nervous, and we got scared. What does a purple flag mean?

Answer

In the standard United States beach warning flag system, a purple flag signifies 'Stinging Marine Life'. This flag is flown to warn swimmers of the presence of potentially dangerous creatures in the water such as jellyfish, man-o-war, stingrays, or sea urchins. Unlike a red flag which may warn of physical dangers like sharks or strong currents, the purple flag specifically targets biohazards. Often, beachgoers are asked to stay out of the water because a high concentration of these organisms can result in painful stings or even severe allergic reactions.