When the Titanic went down, it tipped 1,489 people into the icy Atlantic Ocean, writes Caroline Davis. Although all were wearing lifejackets and the water was calm, none survived longer than two hours. The official inquiry gave drowning as the cause of death in all cases, although evidence pointed to hypothermia.
By the second world war, hypothermia was recognised as a significant problem, but soon came to be seen as the only problem associated with immersion in cold water, said Michael Tipton, professor of pure and applied physiology in the sport and exercise department of Portsmouth University.
"Research shows that the vast majority of people die within minutes," Professor Tipton said. "Two-thirds die within 10ft of safe refuge - and 60 per cent of those are good swimmers."
Contrary to popular belief, he explained, most people who fall into cold water do not die of hypothermia as deaths occur too quickly.
Instead, they are incapacitated by "cold shock", a set of responses seen on initial immersion that include uncontrollable hyperventilation and an increased heart rate that is triggered by a rapid fall in skin temperature and is responsible for most deaths within minutes of hitting the water.
Subjects cannot hold their breath for more than a few seconds, increasing the likelihood of taking in water and drowning. And increased stress on the heart can prompt a heart attack.
Professor Tipton's work has applications from the military through to the oil industry and leisure activities. Up to 10 million people in the UK take part in water-based leisure activities every year and 700 people die by drowning.
Understanding the body's reaction to cold water immersion and subsequently developing appropriate emergency procedures and aids could save many lives.
The research group's latest results will be presented at the International Conference on Environmental Ergonomics in Japan later this year.