July 3, 2025, 9:58 am | Read time: 4 minutes
A renowned marine biologist claims to have made a spectacular discovery off the coast of Mallorca: She reports having seen the rare sea slug Glaucus atlanticus. This would be the first sighting in over 300 years. Due to its extraordinary, almost mythical appearance, it is also known as the “Blue Dragon.” However, as fascinating as this sea creature may be, it should be observed from a safe distance. Find out why on TRAVELBOOK.
Last year, the sea slug Glaucus atlanticus reportedly caused a stir on the beaches of Texas (TRAVELBOOK reported). And yes, that’s an apt description–contact with the so-called Blue Dragon can be unpleasant for humans. Germans should be aware of this, as the marine creature was recently spotted on their favorite island, Mallorca, where it’s currently peak vacation season.
Overview
Blue Dragons on Mallorca–why it’s spectacular
Spanish marine biologist Gádor Muntaner claims to have discovered the extraordinary marine creature during a boat trip in the northwest of Mallorca, specifically near the Serra de Tramuntana mountain range. She reported this to the newspaper “Ultima Hora.” It’s a sensation–no sightings of the sea slug have been recorded on the Balearic island since 1705. “It’s a very, very rare creature,” Muntaner told the paper.
Although not directly on Mallorca, the Blue Dragon has occasionally appeared in Europe and on Spanish coasts in recent years. In 2023, beachgoers in the coastal town of Torrevieja on the Costa Blanca encountered it. The marine creatures were also reportedly spotted in the area two years earlier.
Characteristics of the unique marine creature
The Blue Ocean Slug typically grows between 3 to 5 centimeters. According to “Ultima Hora,” Gádor Muntaner encountered a relatively large specimen. The appearance of the creature is truly unique. Its bright blue body is artfully patterned–the lateral appendages resemble shimmering wings. Normally, the Blue Dragon drifts on the open sea in groups just below the water’s surface. Its striking coloration serves as camouflage, specifically as protection from predators both in the air and in the water. The top side appears deep blue and blends with the sea, while the gray-white underside is barely distinguishable from the bright sky when viewed from below.
Occasionally, however, westerly winds can drive Blue Dragons from the Atlantic to the coasts. Muntaner’s find demonstrates this, as confirmed in a conversation with TRAVELBOOK by marine expert Phillip Kanstinger from WWF. Despite their uniqueness, you should not approach or touch the colorful sea slugs.
What makes the Blue Dragon dangerous
As Phillip Kanstinger explains, the so-called Blue Dragon is a nudibranch. It lives on the open sea, where it primarily encounters cnidarians such as corals and jellyfish, which it also feeds on. “It’s actually good for us humans that the slug eats Portuguese man-of-war, for example,” the expert says, “because they are dangerous.” TRAVELBOOK previously reported sightings of the venomous jellyfish on Mallorca.
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According to Phillip Kanstinger, nudibranchs store the toxins they consume. “This makes them toxic themselves, so you shouldn’t touch them.” Unlike other slugs, they don’t have a hard shell, so the cnidarian toxin is transferred upon contact. The venom of a Portuguese man-of-war causes red, painful welts on the skin upon contact. In the worst case, it can lead to an allergic shock. However, there are no known cases where contact with the “Blue Sea Dragon” has had similar effects on humans. Panic is therefore unwarranted.
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Nevertheless, vacationers should not take any risks if they happen to discover one of the sea slugs on the beach. Leave the creature alone, do not touch it, and if possible, inform lifeguards on site.
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Is climate change driving the Blue Dragon?
Various reports attribute the occasional sightings of Blue Dragons, as well as Portuguese man-of-war, to global warming. According to expert Kanstinger, however, this is still a hypothesis that cannot yet be substantiated. “The animals are only seen sporadically,” he explains, “due to influx events. There is no evidence yet that they are spreading due to climate change.”