Hydro turbines work in a similar manor as other turbines but must be designed
differently due to the differences between sources of power.

http://www.usbr.gov/lc/hooverdam/Gallery/Picnindex.htm

Most power turbines are designed to extract power from the pressure, velocity, and temperature and the interrelation of these factors in a compressible gas.  For hydro turbines there is seldom a temp. difference to gain power from, and the water is incompressible so the design is changed accordingly.

all three above pictures from    http://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/BULB.htm

The left and middle pictures are called bulb turbines and are designed for water heads less that 40m
(in real units 131 ft) they can produce from 10MW up to 100MW (in real units 13,400 to 134,000 hp) of
electrical power.

The picture on the right is a Kaplan Turbine and produces 235MW (315,000 hp) of power from a
57.8m (190 ft) water head

notice how these use one massive turbine blade shaped more like a boat propeller.