The River Boat is a piece of metro-made transport, used by the Nazis, Rangers, and many metro inhabitants, but none more prominent than inhabitants of Venice station. The boat can travel through irradiated waters and is powered by a motor, it uses a railcar frame and uses empty barrels in order to float, it can apparently carry a substantial amount of weight.
The river boats came into being as the surface grew warmer and the melting water sank into the metro, flooding many stations and tunnels. Due to this many stations could not recieve food from other stations farms and began to fish. As a result the river boat was designed for use in flooded metro tunnels and on the surface in swamps. Venice is a great example of where the river boat reigns supreme. It seems to be able to take a lot of damage from mutant shrimps and can fastly move throughout the tunnels.