All marine animals should be assumed to be venomous and treated with great respect. Swimmers, bathers and paddlers are stung by venomous fish even in temperate regions, and noxious creatures abound in tropical seas. Fish toxins are inactivated by immersion in very hot water, and prevention and treatment are described in detail below. Touch nothing unless you are sure it is harmless, and wear stout gloves if you are collecting anything or generally rummaging around in crevices. Collecting living creatures is not only bad news for them, it could be for you too.

The very attractive cone mollusks (Conus spp.) of the IndPacific seas are equipped with a venomous tongue like harpoon tooth. They range up to about 23cm in length, although the majority are much smaller. They have stung collectors through the trouser pocket. Stings can cause unpleasant tingling and numbness, and sometimes even paralysis and death from respiratory arrest. Resuscitation can be lifesaving, but there is no ant venom. Do not collect live specimens.

Octopus saliva contains a vicious toxin that can be introduced into the skin by a bite from the animal’s powerful beak, between the tentacles. Bites are painful and bleed, swell and become inflamed. Blue ringed octopi, Hapalochlaena macula’s and H. undulate of Australia, Indonesia and the Philippines, possess such toxic nerve poisons that they can cause fatal paralysis within 15 minutes of a bite. They are only 10cm long and occur in shallow waters.

The flying squid, Onychoteuthis banksi, is also dangerous, but since it only comes up to shallow waters after dark it rarely comes into contact with people. Those bitten are almost always fishermen. They are sold as food throughout their range; exercise care when preparing them for the table, in case they are still alive.

Jellyfish, sea wasps, Portuguese man-of-war, fire coral, sea anemones and sea nettles all have venomous stinging capsules called nematocysts. Jellyfish stings are most common when there are onshore winds. At worst, jellyfish poisoning causes paralysis of the muscles of respiration. This is transient but lasts long enough to kill, unless someone is on hand to carry out resuscitation.

Worldwide there are about 30 deaths a year due to jellyfish. Just six species are responsible; three of them are the box jellyfish, Chironexspp. or ’sea wasps’. They are box shaped, with tentacles hanging from the four corners of the squares ‘bell’. The largest and most venomous, Chiron fleckeri, inhabits tropical coasts of Australia and Southeast Asia. These fast Swimming jellyfish have bodies as big as basketballs (20cm diameter) and tentacles that trail out for 3m. The tentacles (which carry the sting cells) are translucent, so they are difficult to see and thus easy to brush against by mistake. Those stung experience incredible pain and often collapse and die, sometimes within four minutes. Flooding stung skin with vinegar inactivates any undercharged stingers. There is a specific ant venom in Australia.

Chiropsalmas quadrigatus kills quite often in Indochina seas, from the Maldives to the Philippines. It also occurs in the Atlantic, from Brazil to North Carolina. The fifth lethal species is the Portuguese men-of-war (Physician physicist), which is common in warm waters of the Atlantic, Pacific and Indian Oceans. Finally, there has been one reported death by stings of Stomolophus nomuraiin southeast China, which has a 105m diameter bell. Stay away from big jellyfish wherever you are.

Try to remove any fragments of tentacles, remembering that they can still sting after they have broken off the jellyfish. Vinegar (46 per cent acetic acid) inactivates the stingers of the IndPacific and Australian box jellyfish, but do not use this on other species. A half and half solution of baking soda in water inactivates the stingers of the unpleasant Chrysaora sea nettle jellyfish of the Atlantic. Never ‘treat’ stings by applying alcoholic solutions, such as methylated spirits and suntan lotion: this causes massive discharge of stingers and exacerbates poisoning. Superficial pain usually responds to cold packs or ice applied for 15 minutes. If a victim has stopped breathing give mouth-to-mouth resuscitation and, if necessary, cardiac massage. The effects of the venom are remarkably short lived, so that keeping the victim alive for a few minutes should ensure survival and complete recovery, albeit with scars.

Anemones sting their prey, so treat them with respect. One species, Anemone solvate, found as close to home as the Adriatic coast, can inflict painful stings.Starfish and sea urchins have venomous spines and grapples, which can produce dangerous poisoning. Spines embedded in skin are at best a painful nuisance. Remove them after softening the skin with two per cent salicylic acid ointment, or acetone or magnesium sulphate paste (readily available in pharmacies). This technique may also be useful for extracting deeply embedded pieces of coral.

Adrian vultur writes for holiday illness claim