a fascinating article: this is what happens to your heart when you dive into the sea.

"The moment your face submerges in the sea’s salty waters, a Hulk-like metamorphosis will trigger. Blood will begin rushing from your hands and feet, up your legs and arms, and into your core; your heart rate will reflexively lower 25% its normal rate; your mind will enter a meditative, almost dreamlike-state. If you choose to dive deeper, the transformation will grow more profound until you bear only a passing resemblance to your terrestrial form. You will become a water animal — a fish, essentially. Scientists call this transformation the mammalian dive reflex or, more lyrically, the Master Switch of Life."

"Human blood has a chemical composition 98% similar to seawater. An infant will reflexively breaststroke when placed underwater and can comfortably hold his breath for about 40 seconds, longer than many adults. We lose this ability only when we learn how to walk."