Great catch and good comment. Any floating piece of wood would teach the lesson effectively.
There's not much wood available in those areas aside from the occasional piece of driftwood, but I'm sure if they could make spears and arrows, they could cobble together a boat. Walrus and seal haul out on the Russian coast as well as Alaskan, so their hides would have been seen as a resource at a very early stage. In place of wood, traditional umiats contained whalebone frames. Walking on the ice in the winter is an art. Eskimo have numerous words for "snow" and they would be adept at reading conditions.