Hi, I am trying to find a company that sells a hydro power generator ( The type that is usually trailed behind a yacht by rope or lowered into the water attached to a skeg, and a rotating propellor on the device generates power ). If anyone can help ,with either their proper name so I can google it, or a company that deals with that item I would be grateful.

This article lists 4 main oems - assume that is what you were after?

www.sailmagazine.com/diy/know-how-hydro-generators

Review article here;

www.sailingtoday.co.uk/gear/gear-on-test/hydrogenerators/