" That day, after barely resurfacing from a seventy-two meter warm up dive into the Blue Hole, Mevoli went into cardiac arrest and died. This time, he wasn’t able to bring himself back. When asked to comment on the accident, Natalia Molchanova, regarded by many as the greatest freehold breath diver in the world, said, “the biggest problem with freedivers . . . [is] now they go too deep too fast.” Less than two years later, off the coast of Spain, Molchanova took a quick recreational dive of her
own. She deliberately ran though her usual set of breathing exercises, attached a light weight to her belt to help her descend, and swam downward, alone. It was
supposed to be a head-clearing reset. But, Molchanova didn’t come back either.
And that’s the problem that free diving shares with many other state-shifting techniques: return too soon, and you’ll always wonder if you could have gone
deeper. Go too far, and you might not make it back. "

― Steven Kotler , Stealing Fire: How Silicon Valley, the Navy SEALs, and Maverick Scientists Are Revolutionizing the Way We Live and Work