Tropical coral reefs, especially of the Indo-Pacific region, habour the greatest nymber and diversity of venomous fish. Fish sting by impaling their aggressor on venomous spines which may form part of the dorsal and pectoral fins and gill covers or may be a seperate appendage situated in front of the dorsal fins or on the tail.

Members of the five family of fish have caused human death: shraks and dogfish, sting rays and mantas, catfish, weaverfish, scorpionfish and stargazers. Fish sting produce severe pain and swelling, vomiting, diarrhoea, sweating, fall in blood pressure and irregularities of heartbeat. For pain relief, the stung spine and membranes should be removed to prevent secondary bacterial infection.

Jellyfish, sea wasps, sea anemones and sea nettles belong to a group of animals called coelenterate. The tentacles of these brightly coloured animals are armed with stinging capsules (called nematocysts) which discharge when touched by a swimmer. Such contact can result in transient, burning discomfort and dermatitis.

Severe stings by the Portuguese man-of-war, Chiropsalmus of the Indian Ocean and Rhizostoma of the Altantic causes vomiting, diarrhoea, generalised muscular cramps, paralysis of breathing muscles and fits. Treatment consists of removal of any tentacles after inactivating the toxins in the nematocysts with local application of alcohol, ammonia or even dry sand. Oral antihistamines and analgesics may also be given.