Poisonous fish in the sea: prevention and first aid

Poisonous fish in the sea: prevention and first aid

Prepare yourself for potential encounters with dangerous creatures and learn how to avoid them — these tips could be crucial in saving your holiday and even your life.

Many people have concerns about encountering poisonous and dangerous creatures while on vacation, especially while in the water. But are these fears justified, and how likely is an encounter with a poisonous fish in popular holiday destinations like Croatia or Greece? Knowing what to do in such situations is crucial.

Good news to start with, there are not that many poisonous fish in recreational waters and with a little prevention the chances of encountering them are slim. With our article on sharks, we hope to have allayed any fears you may have had of these majestic guardians of the seas. Now we'll try to do the same with the venomous fish in popular yachting locations of the Mediterranean and tropics.

What you need to know about poisonous marine fish

  • They are usually inconspicuous in colour and blend in with the reefs or bury themselves in the sand.
  • It's their camouflage that's the problem. You simply step on them or touch them unintentionally.
  • Poisonous fish like warm seas. That's why you'll find them almost exclusively in tropical and subtropical waters.
  • Venomous fish are shy. They're more likely to swim away or hide. That's why they defend themselves with venomous spines.

YACHTING.COM TIP: To make sure your preparation is complete, read our most dangerous creatures of the Croatian seas and coastline — both aquatic and terrestrial. 

Poisonous fish in yachting areas

You may encounter these fish while swimming, snorkelling or paddling in shallow water. Learn to identify them.

Toadfish and wrasses

Although kept by aquarists for their unique appearance, toadfish (Scorpaena) and lionfish (Pterois) are relatively unnoticeable in the sea. They camouflage themselves by mimicking underwater reefs and only raise their venomous spines in self-defense. Fortunately, their venom is not fatal to humans, but it hurts a lot and the wounded area is swollen for a long time. In rare cases, respiratory and cardiac problems or nausea can occur.

Where you'll find them: Greece (toadfish), Caribbean, Malaysia, Seychelles, Maldives (lionfish, toadfish)


Toadfish camouflaged in sand and coral

A poisonous fish, the orange-coloured periwinkle (Pterois),



Trachinidae (weevers) also rely on spines with venom glands. These unassuming fish bury themselves in the sand when they feel threatened and erect spines on their dorsal fin. The downside is that, unlike toadfish, they won't even try to swim in front of you. Plus, they like shallow sandy waters, which we humans like. Their venom is not dangerous to humans, but the sting is painful and can cause swelling. In worse cases, dizziness or heart problems can occur. We covered weeverfish in our article about dangerous inhabitants of the Greek seas.

Where you'll find them: the Mediterranean, especially Greece and Croatia.



A stonefish, so called because of its camouflage, which mimics the surface of underwater rocks (Synanceia verrucosa). It hides among the reefs or partially buries itself in the sand and has venom glands on the tips of its dorsal fin, similar to spiny dogfish and toadfish. Its venom is fatal to humans, causing paralysis and cardiac arrest. But don't worry — although up to 1,000 people a year encounter it (mainly in Australia), the vast majority survive thanks to an antidote that needs to be administered within hours.

Where you'll find them: Maldives, Seychelles, Malaysia, limited Mediterranean and Caribbean

Odranec right


For divers, the sight of a stingray (Dasyatis pastinaca, stingray) is irresistible. Although they are peaceful and will swim away from you rather than defend themselves, it is useful to know that their spines are more than 30 cm in length and are equipped with a venom gland. The venom is not life-threatening, but it will cause nausea and headaches. The greater risk is from the stinger itself, which can penetrate deep into the body and even break off.

Where you'll find them: the Mediterranean and the Canary Islands


Silver-cheeked toadfish

Finally, a word of warning for those of you who like to fish on a yacht. In recent years, poisoning by the silver-cheeked toadfish (Lagocephalus sceleratus), which has migrated to the Mediterranean from the Red Sea, has been a problem. This fish is highly poisonous and contains a deadly neurotoxin, similar to the Japanese fugu, to which they are related.

Where you'll find them: the Mediterranean, especially Croatia, Italy, Malta and Portugal

Silver-breasted Chat

First aid for contact with a poisonous fish

Carefully wash the injection site free of sand and dirt. But do not touch it with your hands in case there are fragments of poisonous spines left in the wound. Remove them with tweezers.

Immerse the affected area in as much hot water as you can stand. Hot water helps neutralize the enzymes in the venom. Folk medicine also advises adding vinegar, epsom salt (magnesium sulfate), or even urine to the water. However, scientists have not reliably confirmed that any of these actually help with a venomous fish or jellyfish sting.

Try to remain calm. When you panic, your heart beats faster and distributes the poison further into your body.

Take over-the-counter analgesics like aspirin or ibuprofen to relieve the pain and help with the swelling.

Seek immediate medical attention. You may need an antidote.

Emergency line 112

Too few people still know that there is a single 112 emergency line in Europe. It operates in parallel with national telephone numbers for the police, fire and ambulance services and acts as all three, so you only need to call one number at a time. This model is so useful that it has been adopted by countries such as Egypt, Mauritius, Indonesia, Malaysia, Sri Lanka, Thailand, Costa Rica, the Dominican Republic, Mexico, Panama and many others.

In addition, today's phones are so smart that they automatically switch to local emergency calls when they go to a foreign country's network. The moment you activate it, even on a locked phone, your phone should connect you to the local authorities. But always check the numbers beforehand.

The coastguard will also direct you to the nearest port and hospital if necessary. There's always a contact on the boat. In theory, the company you take out travel insurance with can also help you. However, this is the last option we would try. After all, the insurance company's operators don't have the insight and capabilities of local services.

How to protect yourself from poisonous fish

  • Do not touch wildlife or lure them to you by feeding them.
  • Do not swim too close to the seabed, rocks and reefs. And don't stick your hands in crevices.
  • Get a full-body wetsuit for diving to give you more protection.
  • Wear water shoes with thick, hard soles; the spines of some fish can penetrate weaker ones.
  • Leave plenty of room for fish to escape and don't corner them.

YACHTING.COM TIP: The underwater world is much safer than you might think. And it's definitely worth combining snorkelling and sailing. Try one of our 50 top snorkelling spots

Our boats in the Mediterranean:

Fish in the sea are generally friendly. We can advise you on boats in the top scuba-diving destinations.

FAQ Poisonous fish - first aid