Illustration: Kieran Blakey

The Nuance

There’s a Scientific Reason Why Water Is So Calming

Exploring the ‘Blue Health’ phenomenon and the well-being benefits of oceans, lakes, and other bodies of water

Published in
6 min readSep 3, 2020


Human beings are land animals. We have feet, not flippers. While our body needs water to survive, those needs don’t require that we submerge our heads in H2O.

You might think that diving into water, like peering over a cliff’s edge, would provide a little adrenaline rush. But it turns out that just the opposite is true. “Water submersion has some counterintuitive calming effects,” says Roly Russell, PhD, a researcher at the Sandhill Institute for Complexity and Sustainability and first author of a 2013 Annual Reviews paper on the health benefits of time spent in nature.

When a person’s face is underwater, research has found that heart rate slows and certain blood vessels constrict. Blood is redistributed from the limbs to the brain, heart, and other central organs. Vagal tone and parasympathetic nervous system activity — both of which are associated with the body’s “rest-and-digest” states — are turned up. At the same time, elements of the sympathetic nervous system and the body’s “fight-or-flight” responses tend to mellow out.

Russell says that these physiological shifts are known collectively as the human “dive response” or “dive reflex.” The dive reflex was first observed in marine mammals like seals, and it’s thought to help the mammalian body conserve oxygen when underwater. In people, the dive reflex is especially pronounced in newborns, nearly all of whom will instinctively hold their breath, and whose heart rates will slow, when dunked in water. (Just blowing air on a crying infant’s face is often enough to trigger the dive reflex, which can calm a baby down.)

The human dive reflex is so reliable that ER doctors have used it to treat certain types of heart arrhythmias, including the type that occur during panic attacks. (In one study, they triggered this reflex by asking patients to hold their breath and dunk their face in cold water for 15 seconds.) Some researchers are exploring this and related water interventions as therapies for conditions ranging from anxiety to stroke.



Markham Heid

I’m a long-time contributor at TIME and other media orgs. I write mostly about health. I grew up in Michigan, but these days I live in southwest Germany.