Hyponatremia, commonly called water intoxication, is a potentially fatal condition resulting from extremely high levels of water in the body.Water intoxication can be the result of swallowing large amounts of water during swimming lessons.It is not known whether the actual trigger factor that causes hyponatremia is excessive sodium loss, excessive intake of free water, inappropriate secretion of anti-diuretic hormone or a combination of all these factors. Whatever the cause, the condition is easy to prevent, all it takes is a little common sense and awareness. Repeated dunking under the water and allowing the child to drink the water because their mouth is too close to it should be avoided.The adult must be aware, at all times, of the position of the baby’s mouth in relation to the water surface. In most common cases the baby who has swallowed an excessive amount of water will vomit or pass large amount of urine.This is the body’s way of ridding itself of the excess water. If the child does swallow a lot of water, becomes restless, lethargic, irritable, weak and nauseous and has abnormally wet nappies, they may be suffering from hyponatremia and a doctor should be consulted.