Diving: Hazardous Marine Life

A few of the nasties to watch out for while scuba diving in Tobago's coral reefs

Knowing and recognising marine perils and how to deal with them is critical to a happy and carefree diving holiday. Injuries may be as minor as those caused by a jelly fish or stinging hydroid, but avoidance is better than treatment and every diver should know both courses of action. The following list details a few of the hazards you could come into contact with in Tobago. In all cases you should seek the immediate advice of your divemaster, who will arrange immediate medical treatment when necessary. Never apply fresh water to any marine sting.


Although many jellyfish sting and cause great discomfort, very few are dangerous. A common belief is that the longer the tentacles, the more painful and harmful the sting. The tentacles tend to stick to your skin causing the pain and sometimes nasty scars. In extreme cases the sting can even be lethal. A quick first aid is to pour acetic acid or vinegar over the wound and the creature. Then remove it carefully with a forceps or gloves.

Jelly Fish

Portuguese Man-o-War

Distantly related to the jellyfish, the tentacles of these nasty creatures can reach 50 feet (15m) and are exceedingly toxic. They are normally only found on the surface of the water and are instantly recognisable by their purplish translucent floats. Even when beached and apparently dead, they can be hazardous. The symptoms of a sting vary from mild itching to intense pain, blistering, skin discolouration, shock, breathing difficulties and even unconsciousness. Allergic reactions can be life-threatening. Immediate attention can be given by applying a decontaminant such as vinegar, papain or dilute ammonia, but immediate medical attention should be sought.

Portuguese Man-O-War

Fire Coral

Not actually a true coral, fire coral grows in many different shapes and can usually be identified by a tan, mustard or brown colour and finger-like columns with whitish tips. After contact, a burning or stinging pain develops within 5-30 minutes followed by a red rash with raised wheals and itching. Rinse with seawater - NOT fresh water - and apply tropical acetic acid (vinegar) or isopropyl alcohol then remove the tentacles with tweezers. Immobilise the limb to prevent the venom from spreading. Cortisone cream will reduce and antihistamine cream and tablets will help with the pain.

Fire Coral

Poisonous Sponges

Of some 5,000 species of sponge, only three species produce contact dermatitis and only a dozen species are considered toxic. The red fire sponge (Tedania ignis) and the touch-me-not (Neofibularia nolitangere), amongst others, are laced with abrasive needle-like strands of silica (spicules). These glass shards make a nasty mouthful, and help inject the toxins into would-be predators. If you accidentally touch a red sponge, do not rub the area but remove visible spicules with adhesive tape or tweezers and soak in vinegar for 10-15 minutes. Cortisone cream can help irritation and the pain normally goes away within 24 hours.

Touch-me-not Sponge (Neofibularia nolitangere)

Bristle Worm

Also known as fire worms, bristle worms are common around rocks and coral reefs and often burrow into the sediment or sandy bottom around the rocks or reef. They have segmented bodies with sensory hairs that extend in tiny, sharp detachable bristles. They are found on most reefs. When touched, the tiny bristles lodge in your skin and will cause a burning sensation that may be followed by a red spot or welt. Use adhesive tape to remove the bristles and apply a decontaminant such as vinegar, dilute ammonia or rubbing alcohol.

Bristle Worm

Sea Urchins

Many divers have suffered the highly painful experience of stepping on a sea urchin. The long spines of these spherical invertebrates will puncture the skin, even through a wetsuit, and break off, leaving a painful swollen wound that can go septic if not treated. You must wash the affected part immediately, with very hot water, to soften the spines and make it easier for the body to reject any residue. Treatment with antibiotics will be necessary if the wound goes septic. Sea urchins mainly come out at night and will generally be found in shallow waters with sandy bottoms.

Sea Urchins


This well-camouflaged ambush predator has a long row of venomous spines running down its back, within the dorsal fin. At the base of each grooved spine is a sac of venom, and if a predator bites down on the fish, the venom is forced up a groove in the spine and into the predator. When threatened, the scorpionfish flares the fins, revealing the colours as a warning. If punctured, wash the wound and then immerse it in non-scalding hot water for between 30 and 90 minutes and take pain killers.


Puffer fish

The puffer fish has the ability to swallow water into its stomach and inflate or 'puff' itself into a very large size. When the puffer fish is calm, the spines on its back are hardly visible, but when threatened, the spines are raised and increase the threatening look of the fish. They do this to discourage predator from making them an easy meal. The skin of some species of puffer fish is exceptionally and often fatally poisonous, but normally only when ingested. However, it is a wise precaution to avoid any contact with these fish.

Puffer Fish

Moray Eel

Moray eels are usually brightly marked or coloured. They grow to a length of about 5 feet (1.5m) and are l generally found in rocky areas, under rocks, crevices and ledges. Never put your hands in these areas without first exploring with a probe. They don't normally attack humans unless disturbed. When a moray bites, it refuses to let go. Don't try to free the bite by force as this will tear your flesh. Grip the eel behind the head and apply pressure with finger and thumb until it opens its jaw. Stop any bleeding with pressure, thoroughly clean the wound and seek immediate medical advice to guard against infection.

Moray Eel


Stingrays are bottom dwellers who feed primarily on molluscs and crustaceans. They inhabit the bottom of shallow waters and will regularly be seen resting on the bottom. They often bury themselves in the sand. Stingrays take their name from the barbed spine(s) at the base of their long, whip-like tail. They are perfectly harmless and the only danger is if you stand on them. Injury is uncommon but the wounds are extremely painful and can be deep and infective. Immerse wounds in non-scalding hot water, take pain killers and seek medical advice.



Barracudas are attracted by shiny objects. Attacks are rare and generally only occur in turbid conditions, or poor visibility dive sites, where it is believed that the barracuda has mistaken the diver for prey because of flashing from an underwater camera, dive knife, camera lens or dive light. The risk is higher at night. If bitten, clean the wound, apply antiseptic or antibiotic cream. Anti-tetanus may be necessary. Barracuda can be seen singly, or in schools.



Respect is the word needed should you encounter one of these guardians of the sea. There are many shapes and sizes of shark, but most are recognisable by their triangular dorsal fish. Most species are actually very shy and only a few that are dangerous to humans. Attacks on humans in Tobago's waters are virtually unknown, but care should still be exercised. The scent of blood will give rise to shark attacks, so spear fishing should be avoided. Sharks will seldom attack unless provoked. Many sharks seem to warn you by bumping into you first. Correct action involves a calm ascent back to the dive boat.


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Page Updated: 18 Aug 17