As the craze for cold water swimming continues, Jim Al Khalili talks to triathlete and Professor of Extreme Physiology, Mike Tipton. Is it as good for our mental and physical health as many enthusiasts claim? And do the benefits go beyond a rush of adrenaline causing feel good endorphins to be released in our brains?

Mike studies why people drown. He wants to understand the precise physiological changes that occur when we expose ourselves to extreme environments and to use that information to help save lives. (Shivering and sweating will only get you so far when it comes to temperature control).

Most deaths at sea are caused by the initial cold water shock response, not hypothermia. People gasp for air and swallow lethal quantities of water.

What does the scientific evidence say about the idea that repeated cold water immersion can boost our immunity and have an anti-inflammatory effect?

Mike tells Jim how he came to specialise in this area of science and why he believes we should all be challenging our bodies more.

Producer: Anna Buckley