The Stonefish family Synanceiidae are slow-moving, bottom-dwelling fish that live in shallower parts of the reef among rocks and corals.
Members of this family are mostly thickset fish, with large heads and mouths, and small eyes. The body is covered in bumpy wart-like skin glands and fleshy flaps that can aid with camouflage. Sometimes algae can be seen growing on the body, further improving the camouflage.
Usually found resting on the bottom, buried in sand, or hugging a piece of dead coral, stonefish are masters of camouflage, disguising themselves as rocks and stones, blending almost exactly with their surroundings in colour and form.
Similar to their scorpionfish relatives, stonefish have very sharp, hollow dorsal fin spines, much like a hypodermic needle, each with a venomous gland located at the base.
Stonefish venom is used for self defence, with poison usually injected when an unsuspecting victim accidently leans or stands on one of these fishes. The neurotoxin venom is extremely painful.
The greyish, brownish, reddish Reef Stonefish (Synanceia verrucosa) is the most venomous fish known, and can be found at some of the dive sites around Koh Lanta, especially in and around Koh Haa Lagoon. The Reef Stonefish venom is fatal to humans.
The dark coloured Indian Ocean Walkman (Inimicus didactylus) is also found in and around Koh Haa Lagoon, and is more difficult to spot than the Reef Stonefish. Normally deeply buried in the sand, rare sightings can occur when the fish is walking along the seabed to change locations.
Indian Ocean Walkmans are also commonly known as ghoulfish, goblinfish, sea goblins, spiny devilfish, stinger, and stingfish, and are also dangerously venomous.
We don't encourage people to sit, kneel, walk, or rest on the delicate seabeds around coral reefs, not only due to the very many small and delicate creatures living on the sea bottom, but also due to the very real danger of being stung by one of nature’s most venomous fish.
Stonefish are generally solitary, feeding on small fishes and crustaceans.