As well as skin wood is an obvious material for making a useable hole in the water. At its simplest a single log can be combined into a raft or even bundled brushwood can serve. To add cargo capacity to the single log then wood can be replaced by space to create the monoxylon, dugout or logboat.
I might return to the logboat but in the next post I want to look at what you do with planks, possibly where full-size logs for a logboat are not available.