Spanish beach closed for ‘blue dragons’: how dangerous is this animal and what do you encounter everywhere?

On the Costa Blanca, the police have temporarily committed a swimming ban in the resort of Guardamar del Segura. After all, ‘blue dragons’ were circulating in the water. Which animals are these exactly? Why do they close a beach for that? And where can you bump into them everywhere? Our HLN science journalist Martijn Peters answers all questions.

ttn-3