Transport for London also operates river buses along the Thames; their maps of the London River Services are very much in the Tube map vein, in both tourist and non-tourist versions:
Of the tourist version Ollie O’Brien of Mapping London says this: “We like the pseudo-tube-map styling, although it could of course be simplified even further, with the Thames just being shown as a straight line. The inclusion of isometric squares showing the major landmarks near each pier is a nice touch. TfL has never really decided whether its river services are for tourists or commuters, but this map should satisfy both.”