Ciculatory+System

Heart circulation http://www.smithsonianmag.com/smart-news/box-can-brings-dead-hearts-back-life-180956509/

the mammalian dive reflex Heart rate decreases Blood moves from extremities to organs like the brain

At such depths, blood actually penetrated the cell walls of the organs to counteract the external pressure. When a diver descends to three hundred feet — a depth frequently reached by modern freedivers — vessels in the lungs engorge with blood, preventing them from collapse.

http://ideas.ted.com/2014/06/25/science_of_freediving/

http://www.amazon.com/Deep-Freediving-Renegade-Science-Ourselves/dp/0547985525

http://neurosciencenews.com/blood-type-cognitive-decline-2087/