Since I do not have the book, I do not know how such an experiment could have or would have been conducted or if it is based only upon anecdotal information, it is therefore, hard for me to comment on the graph.

What I will say is, if this was a truly controlled experiment, I question the ethics of individuals drinking seawater to the point of unconsciousness. If the graph describes anecdotal cases (different individuals under varying circumstances) and bases the conclusions upon that information, it is like comparing apples to oranges. Each individual will respond differently, depending upon gender, age, physical conditioning and pre-existing medical conditions.

Pete