Boats with electric motors don't need a dedicated generator, as the motor can act as a generator when you put it in neutral. (If properly configured.)

Super easy to retro fit to be able to pull it out the water when its a light wind too, great for anybody wanting to reduce using their main engine as a battery charger.

Solar is great on sail boats but often the sails block the sun when they are out so its difficult to get full utilisation. Something like a hydro generator works perfectly with a good sized solar install for a sail boat to cover at anchor and under sail.