The Portuguese man o'war, known for its long tentacles and polyps, has been seen on beaches across the US from Texas to Florida. The creature, which can deliver a painful sting even weeks after they've washed ashore, is typically found in subtropical seas and can end up on the Gulf Coast. Lifeguards have warned beachgoers of the danger by flying small red and purple flags to alert them to dangerous conditions on the water. While their sting is rarely fatal to humans, it is recommended for immediate medical attention.