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When I was in the Navy, they used to tell us that the body's resistance could, under certain circumstances, be as low as 300 ohms

Under extreme conditions it appears it can be even less.
http://www.dc.state.fl.us/oth/deathrow/drorder.html

{Scroll down to the table of measurements about a third of the way down the document. The lowest recorded value is 133 ohms.}