While water molecules are polar. They are also very small. One fact not mentioned on the video is that some water molecules are able to squeeze directly through the phospholipid bilayer due to their small size

Simple Diffusion.

Explanation:

The plasma membrane is known as the selectively permeable membrane as they allow the movements of some selected particles only. The movement are facilitated diffusion, active transport and passive transport.

Water molecules are polar in nature. They can pass through the plasma membrane from its region of the higher concentration towards its region of the lower concentration. They move directly through the simple diffusion and does not require any protein or energy molecule to pass through them.

Thus, the answer is simple diffusion.