People have drowned in just 30 millimetres of water
Lying face down, people have drowned in as little as 30 millimetres of water. Drowning is suffocation caused when the mouth and nose sit under liquid, and most fatal cases happen when the person is alone or when anyone nearby fails to notice or cannot help. About 90 per cent of drownings happen in fresh water.
When the airway stays submerged, falling oxygen and rising carbon dioxide trigger a neurological breathing emergency, with mounting distress and occasional spasms of the vocal folds. The word does not always mean death: cases are sorted into those that kill, those that leave lasting harm and those with no complications, the last sometimes called near-drowning. Among children who survive, about 7.5 per cent have health problems afterwards, and even small amounts of inhaled fluid can irritate the lungs and cause fluid build-up over the following hours.
Being unable to swim is a major factor, and formal lessons lower the risk, ideally begun between the ages of one and four. Alcohol is involved in roughly half of fatal drownings and 35 per cent of non-fatal ones. Exhaustion, sometimes from panicked movement or from overconfidently swimming out too far, adds danger, and among people with seizure disorders no cause of death is more frequent than drowning, which mostly happens in bathtubs.
Where people drown shifts with age. Toddlers aged one to four most often drown in home swimming pools, while natural water takes over later; more than half of drownings among people fifteen and older happen in natural settings. In the United States the highest rates fall on children under five and on people aged fifteen to twenty-four. Undetected heart rhythm disorders can also play a part, since cold water or swimming may set them off.
History carries its own warnings. So many early colonists in New Zealand died crossing rivers that drowning became known as the New Zealand death. Recognised prevention steps include swimming lessons, learning to read unsafe water, never swimming alone, flotation devices on boats, fencing around pools and proper supervision, though drowning can happen even where lifeguards are on duty.
Source: Drowning
