Breastshot Wheel
A vertically-mounted water wheel design that is rotated by falling water striking buckets near the centre of the wheel's edge, or just above it, this is known to be breastshot.
Hydraulic Wheel
A recent development of the breastshot wheel is a hydraulic wheel which effectively includes a weir into the centre of the wheel. This was developed by the French inventeur Michael Fonfrede and is commercialised as the Aqualienne with an estimated hydraulic efficiency of 67%, maximum of 76%.