Fascinating, but......

...not necessarily a good choice to read in the middle of the night.

I was reading the bit about George Joseph Smith, the "Brides in the Bath" murderer. Spilsbury researched death from "vagal inhibition", usually induced by choking or strangling, which can act like a karate chop leading to instant unconsciousness. It can also be triggered by a sudden rush of water up the nose, which is what Smith did to his wives (Bessie Mundy, Alice Burnham and Margaret Lofty), by plunging them under the water, his arms under the knees.

If you're thinking of diving feet first into deep water...don't, or at least hold your nose!