Why does a larger propeller turning slowly often provide efficient propulsion?

A larger propeller turning slowly is often more efficient because of the fundamental relationship between mass and acceleration in generating thrust.

A propeller produces thrust by acting on a mass of water and accelerating it. For the most efficient propulsion, the goal is to act upon a large mass of water while keeping the acceleration rate small. A larger propeller covers a greater area, allowing it to engage a larger volume of water with each rotation. By turning slowly, it can achieve the necessary thrust by moving this larger mass of water at a lower rate of acceleration, rather than attempting to force a smaller mass of water to accelerate rapidly.1

Furthermore, operating at lower speeds helps avoid cavitation, a phenomenon where low pressure causes water to form vapor-filled bubbles or cavities that collapse on the blade surface. Cavitation can damage the propeller through erosion and negatively impact overall propulsion efficiency.2