A look inside a micro water turbine.

This device appears similar to the water flow sensor unit, but actually generates a 5V supply from the water flowing through it. The connectors appear to be standard water tap sized connectors (1/2"?) and the unit is directional due to the use of a concentrating orifice to fire the water onto the edge of the blades.
It has an electronic module inside which has a six diode bridge rectifier to rectify the three phase windings of the generator. The output is regulated either by a 78L05 regulator or what appears to be a lithium cell charge regulator.
The turbine rotor is magnetically coupled through a sealed case onto the stator in the dry side of the unit.
The listing states 10W but the 78L05 will not supply 2A! I'd guess this unit will be rated more conservatively around the 1W area or less. I haven't tested it though.