What does a hydroelectric generator looks like?

Water moves through a pipe and spins a propellor of some kind. This spinning is then connected to a magnet, or a series of magnets which rotate inside stationary coils of copper wire. This generates electricity. So there are two spinning parts, the wet part providing the power, and the dry part generating electricity. The whole thing is usually built inside the bottom of a dam, but smaller ones are installed in river channels.