The ‘blue dragons’ are known as ‘the most beautiful killer in the ocean’Costa BlancaSpanish tourists have been barred from going into the water along an entire seven-mile stretch of Spain’s Costa Blanca(Image: Getty Images)

Spanish tourists have been barred from going into the water along an entire seven-mile stretch of Costa Blanca after a rare, poisonous sea creature was spotted.

Reg flags went up on beaches in the municipality of Guardamar del Segura, just north of Torrevieja, following the appearance of so-called blue dragons, which have been branded “the most beautiful killer in the ocean”, writes The Mirror.

The sea slug, also known as Glaucus atlanticus, feeds on the deadly Portuguese man o’ war and other venomous sea beasts.

The dangerous creature absorbs the stinging cells from its food and stores them in concentrated doses, giving it a far more potent sting than its prey.

Those who have been stung by a blue dragon typical experience symptoms such as nausea, pain, vomiting and acute allergic contact dermatitis. On rare occasions it can prove fatal.

Guardamar del Segura’s mayor Jose Luis Saez confirmed the sea ban order this week, and indicated it would remain in place until further notice. On his official X account he wrote: “Red flag on the beaches of Guardamar.

“Bathing is prohibited following the appearance on Vivers Beach of two specimens of Glaucus atlanticus, known as the Blue Dragon.

“We remind people that despite its bright and striking colour and its small 1.5 inch size, they should stay away from this animal because of its sting.

“Guardamar del Segura Town Hall has launched a preventive operation to detect possible specimens carried by ocean currents. Town hall workers are closely following the evolution of the situation and will inform people about the different measures to be taken.

“If you see one of these creatures don’t touch it, even with gloves on, alert lifeguards and other authorities. If you get stung, wash the area affected with salt water and head to your nearest first aid point or health centre.

“These creatures are poisonous and their stings can cause nausea, pain and vomiting. For the time being and until further notice, bathing in the sea is prohibited.”

Lifeguards are expected to remind tourists and locals about the prohibition according to local reports, although sunseekers will still be allowed to head to beaches if they don’t take a dip in the sea.

Following an emergency call about a blue dragon sighting at Santa Barbara beach in La Linea de la Concepcion near Gibraltar on Sunday, six were found on the shoreline and red flags went up. The beach was reopened to bathers the following day, with a yellow warning flag up instead of the red one.