Hydroelectric nets

Today marked the beginning of a class about electric power distribution networks and devices and it made me think about hydroelectric generation. The professor was briefly describing the basic block components of a hydroelectric power dam and it made me wonder if there are any examples in nature of organisms which live off of the flow of a churning river. Are there any plants or bacteria which could produce a voltage? A fuel perhaps?

I pictured a babbling brook with an biological weave of cells spread perpendicularly across to gather the energy of the moving water in some way. It doesn't seem like this idea could compete for large-scale power production on par with a massive hydroelectric dam. Instead, maybe it could be used to power remote small-scale facilities. In any case, it would be an interesting thing to look into.

I don't think the net would block the entire river, instead of would just try to leech off of its flow. If the idea is efficient enough, it probably exists in nature in some way. I'll have to ask somebody who studies living things much more than I do.