[T]he lowest recorded heart rate [of a free diver]... was 7 beats per minute... about 1/2 of someone in a ... - James Nestor

I went to Greece to write a story on ... When most people go underwater... they bail out at ten feet... ears screaming. The freedivers told me they'd previously been "most people." ...To freedive, they said, all anyone had to do was master the art of breathing.

These animals came up to us, welcomed us into their pods and started showering us with these clicks.

[T]he more you focus in on these clicks, the tinier... they get, [growing] into more complex structures. ...[O]ther ns such as dolphins and orcas also use these. It's this secret language... discrete codes... down to the millisecond.