A fish swimming in water uses its fins to push the water backward, making 2 points it swim forward. This is an example of Newton's
law of motion. *

Newton's third law

Explanation:

A fish swimming uses its fins to push the water backward making it swim forward is obeying Newton's third law of motion.

Newton's third law of motion states that "action and reaction are equal and opposite".

When the fish uses its fin to push the water backward, it reacts by being propelled in the opposite direction which is in the forward sense.

The third law is clear indicator that forces are always in pairs. As the fish swims, a net force between the oppositely directed forces do not cancel out.