Could they have used horses instead of people in the age of galleys, or even horses as power for smaller boats like harbor tenders and tugs during the age of sail? https://en.wikipedia.org/wiki/Horse_mill
They were and still are.
Horse drawn canal barges of coal were a major part of what allowed the industrial revolution to take place.
A horse can pull a far larger barge of coal over water than it can a cart over land.
They're still used for pleasure journeys here in the UK.