Why you have no excuse not to get in the sea this winter

It’s official! As humans, we have an innate response to help us deal with being exposed to cold water. This means there is no excuse for you to avoid learning to surf at our Bude surf school this winter. Justin Bieber himself once said he’d jump into cold, cold water – it’s time for you to do the same!Just one of the spectacular views that await your visit to Ireland

The mammalian dive reflex is what allows sea-dwelling creatures to spend so much time underwater in between breaths. It is a natural reflex in response to cold water that essentially stops blood from going to the limbs, creating a brain-heart circuit to conserve oxygen. It has been found that humans too exhibit this behaviour, meaning there’s no excuse not to get out and about in the sea this winter!

The mammalian dive reflex is a physical response to when cold water touches the face and optimises respiration. The response is much stronger in water-dwelling mammals such as seals, otters, dolphins and other marine animals than it is in humans, although babies have a stronger reflex. When the face, or particularly the nose and forehead, is exposed to cold water, a three-part sequence is initiated with the aim to conserve oxygen.


The first, nearly immediate response is a slowing of the heart rate. The heart rate slows by between 10% and 25%, reducing the body’s requirement for oxygen in the bloodstream and allowing the air to be used by other organs. It’s even possible to train for increased bradycardia, and divers may encourage responses by doing breath holds in a bowl of iced water. Seal’s heart rates can slow by over 90% on an extended dive, beating as little as ten times per minute.

Peripheral vasoconstriction

This is where the blood vessels in your hands, feet, arms and legs begin to constrict, shifting more blood to the core of the body, meaning that vital organs can be prioritised. This can also be observed out of the water if you repeatedly hold your breath, and can often cause cramp.

Blood shift

The third and final response can rarely be witnessed in humans, except in extreme freediving situations. The blood shift means that as lungs compress, blood vessels around the alveoli expand with blood to compensate for the reduced volume of the lungs.

Most of us will only ever experience the first, and possibly the start of the second, stages of the mammalian dive reflex when our face comes into contact with cold water or is submerged. This will usually entail a sudden increase in heart rate as our body is shocked by the cold, followed by a noticeable decrease as the effects of bradycardia begin to take place. Over time, this is followed by the numbing of hands and feet.

As the days get shorter and darker and we are plagued with sub-zero temperatures, a dip in the sea seems nothing short of insane. However, humans can and do experience far colder waters than we get here in Cornwall. I don’t think Sir David Attenborough would take too kindly to his Planet Earth Antarctic camera team refusing to film cutting edge footage because they are a little bit nippy. Although sitting at home with the heating on full blast and a classic Christmas film on may seem more appealing at the moment, once you take the plunge you certainly won’t regret it.

Come on down to Outdoor Adventure and put your mammalian dive reflex to the test with any of our water-based activities.