Surf forms when waves reach shallow water and slow down until they crash forward. Most shores are exposed to some form of surf, so if you plan on diving from the shore, you need to know how to judge surf conditions and plan an appropriate entry and exit.

Beaches with gentle slopes experience spilling breakers over a long distance. The area where surf breaks is called the surf zone, and can be difficult to pass through when waves are large or close together.

On steep beaches, the surf is more likely to break close to the edge of the water. These are called plunging breakers, and their surf zone is short in comparison to other types of surf. However, they are very powerful, and should be avoided unless they are small enough to make a safe passage.