That is true, but you impart the energy on water to move forward through the use of propeller. likewise, you'd need water to be moving (energy) against an impeller which has resistance to generate the electricity.
Put simply,
The British scientist and author C.P. Snow had an excellent way of remembering the three laws:
- You cannot win (that is, you cannot get something for nothing, because matter and energy are conserved).
- You cannot break even (you cannot return to the same energy state, because there is always an increase in disorder; entropy always increases).
- You cannot get out of the game (because absolute zero is unattainable).
src:
https://www.physlink.com/education/askexperts/ae280.cfm
