Dangerous Marine Animals of Koh Tao

Here you can find a list of the animals, both on land in the water, that you should be careful around. This is provided not to scare you, but to improve your safety by informing you what to watch out for, and what to do if you encounter some of these species. Please note that we have never had a conservation student injured by any of these marine species, and want to keep it that way. So learn what to avoid and stay safe while you are having fun enjoying Koh Tao!

 

The devil scorpionfish, Inimicus didactylus

The devil scorpionfish, Inimicus didactylus

General notes on marine stings, bites, and toxins

Most dangerous animals encountered while diving do not ‘attack’ humans, and are easily avoided by practicing good buoyancy and not contacting the reef. In general, a hands-off policy will keep you safe at all times. However, in Conservation Diving we must sometimes handle marine life or kneel on the sandy sea beds while doing artificial reef work, so divers must always pay attention. The following rules will ensure your safety:

  • Know which animals are dangerous and how to avoid them
  • Know what to do if stung/bit
  • Never touch anything unless instructed to do so
  • If you don’t know what it is, don’t touch it
  • Never collect marine life or shells

Also, marine bites or stings while diving carry the added risk of panic and diving related injuries, so if you are stung or biting follow these steps:

  1. Don’t Panic – Stop what you are doing, breath, and think before doing anything else. DO NOT ASCEND
  2. Signal to your buddy/dive leader that you are having a problem
  3. If possible, also point out the animal to your dive buddy/leader so they know what precautions and treatment should be taken
  4. Perform a controlled ascent, with your buddy, of no more than 9 meters per minute (DO NOT do a safety stop)
  5. Inflate your BCD, signal to the boat, and request assistance

 

As with any problems you could potentially have while diving, the most important thing is to always stay calm. Little problems can quickly become big problems when people panic. To prevent panic, know yourself, know your limits, and have a plan for what to do in case of injuries and emergencies.

Stop, Think, Plan, Act

Jelly fish

Jellyfish

Species Observed on Koh Tao:

There are several species of jellyfish on Koh Tao, most of which are in fact not harmful. However, in recent years there have been sightings of several poisonous species of jellyfish, including Box Jelly fish (chirodropids and carybdeids). The Portuguese Man-of-War is also a danger in many parts of the world’s oceans, but has only been spotted one time on Koh Tao.

Frequency of Encounters:

Vary Rare (observed only a few times per year)

What to Watch out for:

Jellyfish drift slowly through the water, and are thus easily avoided by divers paying attention. In most cases, stings result from people trying to pick up or handle a jellyfish, thinking it is not dangerous. If you encounter a jellyfish under water, maintain a safe distance. Also, the use of rash guards or wetsuits is strongly encouraged while diving, snorkeling, or swimming around Koh Tao.

What to do if Stung:

Do not remove tentacles with your hands, instead flush them off with sea water. Immediately wash the affected area with vinegar and seek medical attention.

 
conesnail

Cone snails

Species Observed on Koh Tao:

Cone snails are a very diverse group of marine gastropods. Although most are not poisonous, the ones which are contain some of the most dangerous and potent toxins on the planet. All species should thus be avoided and never handled.

Frequency of Encounters:

Common to all sites around Koh Tao, especially deeper than 12 meters, occasionally also wash up on the beach.

What to Watch out for:

The cone snail has a ‘harpoon’ which it uses to kill and eat fish or crustaceans, the barb of this ‘harpoon’ contains the powerful neurotoxins. The cone snails will allow sting you if you handle them, so never pick-up or touch a cone snail, even if you think it is dead.

What to do if Stung:

There is no anti-venom for cone snail toxins, follow the steps at the beginning of this chapter and seek medical attention immediately.

 

Toxic sea urchins

Collector Urchin
Species Observed on Koh Tao:

The collector urchin, also known as the flower urchin (Toxopneustes pileolus)

Frequency of Encounters:

Common in reef areas such as Chalok Ban Kao

What to Watch out for:

The collector urchin is hard to spot as it often covers itself in rubble, sponges, and other debris. Also have a good look before kneeling down in the sand, or around the giant clam nurseries, and while collecting coral fragments for the coral nurseries.

It is, in fact, not the spines which are dangerous, but the round suction cups, called pedicellariae, they are actually little claws which close up injecting venom into whatever has tried to touch it. In humans, effects begin several seconds after being injected, and generally include excruciating pain and paralysis, lasting up to 6 hours.

What to do if Stung:

Notify your buddy and immediately begin a controlled ascent to the surface. Inflate you BCD and call for help. Swimmers are thought to have drowned after being paralyzed by the toxin, so be sure somebody knows right away that you require assistance.

 
Raggy Scorpionfish

Stone fish/Scorpionfish

Species Observed on Koh Tao:

There are several species of stonefish and scorpionfish on Koh Tao, all of which are thought to be poisonous. The most common species encountered are the raggy scorpionfish (Scorpaenopsis venosa) and the Devil Stinger or Indian Walkman (Inimicus didactylus). Stonefish are camouflaged to closely resemble features on the reef, and are very difficult to spot.

Frequency of Encounters:

Common, seen every few dives (if you have a good eye for them)

What to Watch out for:

The fins on the back of the fish contains the toxin, which is injected when a person steps onto or grabs the fish. As one of the most venomous fish in the world, the toxin causes long-lasting pain and secondary problems involved with swelling in infections. In some cases the sting can also be fatal. Most stings occur from people walking on the reef, but occasionally divers kneel on or put their hands onto the fish. Avoid this by refraining from walking on the sea bed and not grabbing onto rocks or dead coral while diving. During conservation activities always check coral fragments and structures before you touch them, and keep an eye out for these fish. If you do happen to see one on an artificial reef, be sure to let the other divers working with you where it is. The sign for stonefish is to point with your little finger or a closed fist (danger).

What to do if Stung:

There are no anti-venoms for stonefish, although medical facilities can treat some of the symptoms. Victims have reported unbearable levels of pain associated with stings, which can cause fainting or shock. In some cases symptoms can last several months. It is vital that you remain calm and still perform a controlled ascent from the dive, get quickly to the boat where you can be treated for shock and transported to a hospital.

 

 
COT

Crown of Thorns starfish

Species Observed on Koh Tao:

Acanthaster spp.

Frequency of Encounters:

Very common (multiple individuals seen on each dive)

What to Watch out for:

The spines covering the Crown of Thorns Starfish are not technically poisonous, but do cause great pain and discomfort if they enter the body. Some victims may also experience shock if they are allergic to the sting. Avoid handling these starfish, and watch your buoyancy and you will have nothing to worry about.

What to do if Stung:

Keep calm, although the sting is very painful, it is generally not life threatening. Massage the affected area, starting from close to the heart and pushing towards the wound to force out any toxins or pieces of the spines. Perform a controlled ascent and the put the affected area in hot water on the boat for 20-30 minutes.

 
Trigger_Titan_2

Titan Trigger fish

Species Observed on Koh Tao:

Multiple species, the most problematic of which is the Titan Triggerfish (Balistoides viridescens)

Frequency of Encounters:

Common (seen on most dives, but rarely a problem)

What to Watch out for:

The titan triggerfish is a large fish that will become quite territorial and defensive during nesting season. Their territory can be imagined as an upside cone, which starts from the nest and gets wider up towards the water’s surface. Generally, the triggerfish will begin swimming erratically and putting up its ‘trigger’ to let divers know they are too close. Divers who fail to recognize these signs, or are not looking out for the fish, can be attacked. Generally the fish will ram or hit the divers, but in some cases can also bite. This is not life-threatening, but can be quite scary.

What to do if attacked:

First, do not panic or go up. Fast movements look threatening to the fish, and going up not only puts you in danger of decompression injuries, but also puts you more into their territory. Turn and face the fish, put your fins between you and the fish, and begin swimming backwards to get out of their territory.

Centipedes

What to Watch out for:

Centipedes generally live in the dead leaves on the jungle floor, but have also been known to explore bedrooms, BCDs, and Shoes. They deliver a painful bite, which can induce anaphylactic shock in rare individuals who are allergic. If you are bitten, wash the area with water or saline and go to the clinic for treatment and pain relievers.

Dogs

What to Watch out for:

Dogs on Koh Tao are notoriously friendly and welcoming, spending most their days lying on the beach and playing with the tourists. However, some dogs are unpredictable and can bite, so always be careful. If you are bitten, notify the dive school so we can contact the owner of the dog and ensure it is current on all vaccines. Rabies is rare for the region, but in some cases it might be necessary to receive precautionary treatment at the clinic.

Snakes

What to Watch out for:

Poisonous snakes are very rare on Koh Tao, however since they are difficult to tell from the non-poisonous ones it is best just to keep your distance. The green tree snake blends in well with the jungle, so take caution when trekking or hiking on the island.

Mosquitoes

What to Watch out for:

Mosquitoes cause more problems for our conservation students than any other animal on Koh Tao. Apart from being annoying and itchy, mosquito bites can become infected if not properly cared for.  Be sure to keep wounds clean and try, and also cover every wound with cotton gauze to prevent infection by dust or small flies. Occasionally mosquitoes on Koh Tao carry Dengue Fever (Malaria is historically not a problem on Koh Tao), if you feel you are coming down with a fever please visit a clinic and contact our staff immediately so we can talk to you about treatment options. Avoid mosquitoes by using bug spray, staying near a fan or indoors during early morning and late afternoon, wear a shirt and pants when going hiking in the forest, and sleep with a fan on you all night.

 

For more information about marine animals of Koh Tao Check out some of our other Learning Resources pages:

LR3 Reef fish

 

 

 

LR6 Inverts