Class 0-> No current, flat water.
Class 1-> Flat water current, no
drops.
Class 2-> Trains of waves, soft
currents both wide and narrow.
Class 3-> Longer trains of larger
waver, fast and strong currents (narrow and wide) both
straight and with curves.
Class 4-> Drops (ramps) with large
rapids, very fast and strong currents, with possible
fast turns and sudden changes of direction.
Class 5-> Large drops (3-4 meters)
free-falls.
Class 6-> Waterfalls, drops from
5 to 12-14 meters.
Class 7-> Impassable. Very dangerous
currents (blocked underwater passages, blocked rapids,
etc.) For example: Niagara Falls …