Blue dragon, glaucus atlanticus. Credit: Sylke Rohrlach / Wikimedia Commons / CC BY-SA 2.0
Authorities have issued a red flag warning and temporarily banned swimming along parts of Spain’s Costa Blanca after sightings of venomous sea creatures known as blue dragons.
The marine animals, which have appeared along the shores of Guardamar del Segura just north of Torrevieja, are small but dangerous.
Though barely 1.5 inches long, the creatures carry venom potent enough to rival the sting of the Portuguese man o’ war, a much larger and more feared jellyfish. Blue dragons feed on these jellyfish and store toxins, which they use for defense.
Two specimens of Glaucus atlanticus, commonly referred to as blue dragons, were discovered this week on Playa Vivers, a beach located between the mouth of the Segura River and Babilonia Beach. In response, lifeguards raised red flags and began using loudspeakers to warn beachgoers to stay out of the sea.
Fewer swimmers are seen, but crowds remain
Despite the bathing ban, many people continued to visit the beach on Wednesday, although significantly fewer entered the water.
Mayor Jose Luis Saez confirmed the swimming restriction in a statement on the social platform X, adding that it would remain in effect until the situation is fully assessed. According to him, the red flag would stay in place for 12 to 24 hours, depending on developments.
Two deadly blue dragons, or Glaucus atlanticus, prompted the closure of beaches in Guardamar del Segura, Spain, on August 20, as officials warned swimmers to avoid contact; they later reopened with caution but maintained vigilance against the toxic creatures. pic.twitter.com/Y6h2VnTVQ6
— Nyra Kraal (@NyraKraal) August 22, 2025
Saez advised the public to avoid contact with the animals, stressing that their bright color and small size do not make them harmless. He noted that touching one, even while wearing gloves, could lead to painful stings and serious symptoms such as nausea, vomiting, and skin reactions.
Coastal patrols launched for further sightings
To monitor the situation, Guardamar del Segura’s local government has launched a coastal sweep to identify any additional sea creatures carried in by ocean currents. Municipal workers are actively patrolling the area and coordinating with lifeguards to enforce safety measures.
Meanwhile, sunbathing is still allowed on the beach, though entering the water is strictly prohibited. Tourists who ignore the ban risk fines, as officials work to prevent injuries caused by these toxic animals.
Similar warnings were issued earlier in the week at Santa Barbara Beach in La Línea de la Concepción, near Gibraltar, after six blue dragons were found. That beach reopened the following day under a yellow caution flag.
Though rarely seen, blue dragons have appeared on shores worldwide—from Spain to Australia. In 2018, experts in Sydney warned the public after large numbers of the creatures washed ashore.
Earlier this year, Spain also experienced a separate marine event when thousands of blue jellyfish, known as by-the-wind sailors, covered Playa del Cura in Gran Canaria.