When my wife was pit crewing my Yukon River races, shw had the opportunity to sit with First Nation residents while waiting for us to pass. Most have never learned to swim, unlesss they attended school in Whitehorse which has a large athletic complex with a pool. The silt in the river, especially below Lake Laberge and the confluence of the Teslin it is so thick that it clings to everything and fills pockets and clothing, weighting them down. You cannot see a millimeter into the water and when paddling through, as it sounds like sandpaper or mistuned AM radio static on the bottom of the canoe. Few survive falling into the near freezing waters at any time of year, as my wife was told.