Steam riverboats travel up and down the Thames in Syndicate. You cannot steer them; instead they work as moving platforms you run and jump across to cross the river without swimming.
Industry has left the Thames badly polluted, so hopping from deck to deck is the better way over. Boats are platforms only: you climb and run across them, you never take the helm.
Some memories take place on boats, such as Operation: Dynamite Boat for Queen Victoria, and the Thames borough's Templar hunts include Captain Hargrave, who patrolled the river.