Kayak
Your best overland solo-adventure friend. Of course, being the only boat that can be carried as an item helps. It's the fastest boat for a solo player, and very maneuverable!
To carry the kayak, just break it.
Kayak
Kayaks are the smallest and most portable boats.
Soak a Large Prepared Hide in either tallow or olive oil to make its surface impervious to water.