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Water safety (waterborne diseases and immersion)


(Published June 2005, last reviewed with no updated 2015)


An awareness of the possible dangers associated with water activities should not be allowed to interfere with the challenge associated with these activities. Proper training in the background to the dangers and self help techniques of survival can help to eliminate or minimise the dangers.

Self help in cold water immersion

If there is any danger that a person will be in a position where cold water immersion is possible, the wearing of a life jacket or buoyancy aid and, if
possible, some protective clothing, i. e. wet or dry suit, or thermal type wear, is recommended. If actually immersed, movement should be minimised. If by oneself, the adoption of the Heat Exposure Lessening Position (HELP) will minimise heat loss (see above right). By adopting this crouching position, the areas of greatest heat loss (the head, neck, sides and groin) can be protected.


If a group of people find themselves in cold water together, they can adopt the HUDDLE position. In this, the sides of the body and the lower body
areas are pressed together. As well as reducing the heat loss there are advantages mentally in being together. Any young person should be placed in the middle of the huddle.


Practicing drown-proofing in cold water exposes the head to the cold water, increases the rate of body cooling, and hastens hypothermia. Treading water uses up body energy which means that heat is being lost more rapidly than if simply floating in your lifejacket or buoyancy aid. Any person
regularly undertaking water activities in water which has a temperature of less than 15C, should practice H.E.L.P. and Huddle techniques regularly, so that if there is an emergency they come automatically to mind.


Hypothermia is an insidious condition that creeps up slowly on the victim. If a casualty has been immersed in cold water for more than a few minutes it is wise to consider the possibility of hypothermia. It's also possible for people involved in water activities to succumb to hypothermia just by being exposed to cold, damp conditions in an open boat, canoe or sailboard.

Weil's Disease

Weil's Disease is a bacterial infection carried in rats’ urine which contaminates water and wet river banks. The bacteria does not survive for long in dry conditions. It can be a serious illness requiring hospital treatment, and can lead to kidney or liver failure. Weil's Disease is a notifiable illness. The bacteria are absorbed through the skin or mucous membranes of the mouth and eyes. It gets into the blood stream very easily if you have a minor cut on your skin or feet, if you become immersed. If you feel ill after training - particularly in stagnant water or pools - or have any of the following symptoms, call your doctor promptly. The most common early symptoms are high temperature, an influenza-type
illness and muscle pains. Tell your doctor that you have been undertaking water activities and where and ask if you can have a blood test for Weil's Disease.

There is a specialist reference laboratory for Leptospirosis in the UK, which can be consulted by doctors.

Blue-green algae

Certain species of the blue-green algae can produce toxins which, upon contact, may cause a number of conditions such as dermatitis, asthma, eye irritation, rashes, blistering of the skin around the mouth and nose, nausea, gastroenteritis, muscle cramps, headaches and pneumonia in some people.

They have also caused fatalities in fish, livestock and pets. These organisms can undergo a very rapid population increase in favorable conditions (i.e.
prolonged, warm, still weather and high levels of nutrients in the water such as nitrogen runoff from fertilisers used on adjacent land) and therefore, produce very high levels of toxin quite suddenly. This is sometimes, but not always, associated with the production of a scum at the surface of the water.

Other potential hazards