How does a ship's propeller create forward thrust to move the vessel?

A ship's propeller creates forward thrust by accelerating a mass of water backward, operating on the fundamental principle of Newton's Third Law of Motion. The propeller consists of a central hub from which several blades extend. Each blade is designed with a specific curved and angled shape, much like a twisted wing, known as its pitch, optimized for moving through water. When the ship's engine rotates the propeller shaft, the blades spin through the water. As a blade rotates, its angled surface pushes against the water. Due to the blade's shape and rotational motion, it acts like a rotating wedge, deflecting water from in front of it and accelerating it rearward, or sternward, behind the propeller. This action creates a region of higher pressure on the aft (rear) side of the blades and a region of lower pressure on the forward (front) side of the blades. The difference in pressure, with higher pressure pushing from behind and lower pressure pulling from in front, contributes to the forward force. According to Newton's Third Law, for every action, there is an equal and opposite reaction. The action is the propeller pushing a column of water backward with significant force and velocity. The equal and opposite reaction is the water exerting a forward-directed force on the propeller, and consequently on the ship itself. This forward force is known as thrust, which propels the vessel. The process is analogous to how a screw advances into wood when rotated; the propeller 'screws' its way through the water by continuously pushing it backward.