The information you are looking for is in the chapter titled "The Zero-Moment Point." The entire chapter deals with the subject of drowning, so there is not enough space here to "post" the description, as you ask.
The title refers to "the point of no return," that is, the moment at which a boat begins to capsize. The author describes what that moment is like and what happens when a boat is flooded. He then describes what it is like for the crew members on that flooded boat.
Some critics have said that he is too detailed, maybe even ghoulish, in his detailing the stages of drowning. He begins with the first instant when the men hit the water: "it's cold, but not paralyzing." Then he describes the instinct not to breathe in water: "The instinct not to breathe underwater is so strong that it overcomes the agony of running out of air." Then he describes the body's need for oxygen: "At that point there's so much carbon dioxide in the blood, and so little oxygen, that chemical sensors in the brain trigger an involuntary breath whether he's underwater or not." The rest of the chapter continues on to describe the panic and pain the drowning person experiences.