Hazardous creatures of the deep; what marine life should you avoid when snorkelling and diving abroad.

As you are probably aware of by now, we’ve opened our very own set of STA Travel Clinics. Little hubs of travel health information where you can talk to trained medical professionals about anything related to your health when preparing to go travelling.

Over the past few months, trained nurse Michelle Sellors has been a regular contributor to the STA Travel Blog in our ‘from the travel clinic’ series where she’s talked about everything from Malaria to Diarrhoea, and she’s back! This week Michelle is going to be sharing some advice for snorkelling and diving, giving you tips on what to look out for in the water to avoid any painful mishaps with these critters of the sea.

Beware of Jellyfish!

Keep your Eyes peeled for these sea creatures next time you’re in the water abroad


The tentacles of jellyfish are covered with cells called nemocysts which contain venom. The greatest risk with most jellyfish stings is a severe allergic reaction. Box jellyfish, however, are considered one of the most dangerous sea creatures with venom potent enough to kill. In fact, they are thought to kill more people each year than sharks and crocodiles combined!

Irukandji are tiny jellyfish only about 2cm across which can still give a nasty sting. Extreme pain isn’t usually felt until 20-30mins after the actual sting. First aid for jellyfish stings is to rinse off tentacles with hot water. If heated water isn’t available use sea water rather than fresh water. Carefully remove tentacles with gloves or tweezers- the nemocysts can still even when not attached to the jellyfish.

Vinegar is still used to treat box jellyfish stings although there has been some debate on it’s usefulness in recent years. Immersion in very hot water is recognised to reduce the pain. Over 102°c is recommended but as a general rule of thumb as hot as you can stand without scalding.

Cone Snails

As pretty as they are it’s a potentially hazardous pastime to collect cone shells in tropical waters. These molluscs have a harpoon-like dart which can inject potent venom.
It’s said that there is enough venom in one Geographer Cone to kill 700 people! Luckily these creatures tend to hunt at night. Avoid picking up live cone shells and don’t be tempted to put one in your pocket. Thick shoes are recommended for walking on reefs.

Cone snails can leave a nasty sting.


There are various species of venomous fish but perhaps the most significant is the stonefish. These fish live on the sea bed of tidal inlets and are very well camouflaged- they do indeed look just like encrusted stones. As a defence against predators they have a row of 13 venomous spines along their back.

The unwary wader can easily stand on one of these fish and the resulting sting can cause excruciating pain. The venom can also affect the respiratory and heart muscles and led to paralysis.

The treatment for stonefish stings is immersion in very hot water for 30-90mins. Some countries keep supplies of stonefish anti-venom to treat severe cases. Avoid being stung in the first place by wearing thick soled shoes and stepping very carefully!

If you stand on a Stonefish - you'll know about it!


Scrapes and cuts from coral are one of the most common injuries for swimmers, snorkelers and divers in tropical waters. Abrasions can be painful, inflamed and easily become infected.

Protect yourself in the first place by wearing appropriate clothing and consider swimming footwear. If you do get a cut, wash it well with soap and water and remove any fragments of coral that can become embedded in the skin. Seek medical advice if the cut remains red, painful and inflamed- antibiotics might be necessary.

If you get a raised red rash, burning sensation and itching immediately after a coral scratch then it might have been fire coral which isn’t a true coral but a hydroid- a stinging creature related to jellyfish.

If you’re off travelling soon, book an appointment at one of our STA Travel Clinics to make sure you have discussed you’re travel health with one of our fully trained nurses before you go – book an appointment on our website now!