Upstream motorized travel is defined as travel by any type of motorized vessel predominately against the current through Cataract Canyon as defined above. Motorized vessels are permitted to use eddy currents in rapids to re-run the tail- waves of the rapid. The beginning of the rapid is where the current speed increases dramatically, or the area known as the “tongue”. The tongue of a rapid is the “v” shaped patch of smooth water that has not yet been aerated by the wave action.