Tiny, beautiful — and dangerous: the blue dragon stores stinging cells from prey like the Portuguese man o’ war, delivering a painful sting. Recent sightings off Guardamar del Segura (Costa Blanca) triggered red flags, later eased to yellow with warnings not to touch specimens.
Credit : Sahara Frost, Shutterstock
Holidaymakers in Guardamar del Segura were told to stay out of the sea after lifeguards raised red flags along a seven-mile (11km) stretch of the Costa Blanca.
The culprit wasn’t rough surf or a shark sighting, but a tiny, dazzling sea slug with a nasty party trick: the blue dragon (Glaucus atlanticus).
By today, the all-out ban had eased to yellow flags – swimming allowed, caution advised – yet authorities are keeping patrols in place and asking beachgoers to report any sightings immediately.
What is a ‘blue dragon’ and why do lifeguards take it so seriously?
At first glance, a blue dragon looks like something from a fantasy film: electric-blue frills, silvery body, barely 4cm (about 1.5in) long. But it’s not a toy for a beach selfie. This slug feeds on venomous drifters including the Portuguese man o’ war, then stores and concentrates their stinging cells inside its own body. That “recycling” makes its sting more potent than the original jellyfish.
Touch one – even accidentally, even with gloves – and those cells can be fired into your skin. Typical reactions include intense pain and burning, nausea and vomiting. For children, anyone with allergies, or people with heart or breathing conditions, a sting can be dangerous, and multiple stings escalate the risk. That’s why, when two specimens turned up on Vivers Beach, Guardamar’s mayor José Luis Sáez ordered a swift no-bathing order and a preventive sweep of nearby sands.
A quick myth-buster: blue dragons aren’t fish, and they aren’t jellyfish. They’re pelagic nudibranchs — sea slugs that float upside down on ocean currents, their blue backs camouflaged against the water’s surface. When winds and currents push their prey shoreward, a few of these hitch-hikers can arrive too.
Where they’ve appeared – and what the beach flags mean
The first closures came just north of Torrevieja in Guardamar del Segura, after those two blue dragons were spotted on Vivers. Patrols and council crews set about checking the tide line and watching for more. Further west, La Línea de la Concepción (near Gibraltar) briefly shut Santa Bárbara beach on Sunday after a report to police; six blue dragons were found on the shoreline. That beach reopened the next day under yellow flags.
Guardamar has now moved from red to yellow, but the town hall says lifeguards and local police remain on alert and will update warnings as conditions change. You can still bask on the sand; you just need to treat the water with caution and stay close to the supervised zone.
If you’re new to Spain’s beach code, a quick refresher:
Red flag = no bathing. Not a suggestion — you can be fined for ignoring it.
Yellow flag = bathing with caution. Risks are present; it’s safest inside the lifeguard sector, and you should keep children within arm’s reach.
Spot one? Here’s what to do – and what not to do
The advice from local authorities is refreshingly simple:
- Don’t touch it. Not even with gloves. Blue dragons can still sting after death; gloves don’t guarantee a seal against the cells.
- Call for help. Alert lifeguards straight away and keep others — especially children — away from the area.
- If you’re stung:
- Rinse with seawater, not fresh water. Fresh water can cause more stinging cells to rupture.
- Don’t rub the skin, and don’t use vinegar or alcohol.
- Gently remove any visible tentacle bits with tweezers or the edge of a card.
- Go to the first-aid point or nearest health centre. If there’s trouble breathing, swelling of the face or throat, chest pain, fainting or a widespread rash, treat it as an emergency.
A few extra tips to keep your day on track: ditch the rock-pool exploring while yellow flags fly; flip-flops help when wading the shallows; and keep an eye on lifeguard loud-hailer announcements. Most encounters amount to nothing more than a sighting – but respect the flags and you won’t miss half your holiday at a clinic.
So, why now? Blue dragons follow the food. Warm surface waters, wind patterns and blooms of jellyfish/man o’ war can nudge both prey and predator towards beaches. Most drift back out; a few wash in. Because they’re rare, lifeguards take a “better safe than sorry” approach when specimens appear, especially during busy August weeks when shores are packed with families.
For Guardamar, that meant seven miles of red flags until crews were satisfied the risk had eased – and a measured shift to yellow once it had. “Municipal services, police and lifeguards remain alert,” the mayor said, thanking beachgoers for cooperating and promising updates as needed.
Sun, sangría and a sensible look at the flagpole should see you right. Enjoy the sand, keep your distance from the sea’s “most beautiful killer”, and you’ll still have a cracking day on the Costa Blanca.
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