you put hunted animal in the river to bleed it out (through immersion in moving water) and to cool it down so it rot slower.
to keep it warm is to make it rot faster. and the imagery was closer to a pond than river which "do not drink still water" comes to play.
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they have freakin salt and didn't know how to make jerky or preserved salted meat?
and they don't remove the fat layer? not sure about the norm on curing but fat have a lot of other function. "Ascendance of bookworm" goes pages on removing fat, process it, and storing it.
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and yes, drinking alchohol makes you "feel" warm but its actually lower your core body temp which are bad in winter scape like that.