The seashore can be divided into zones based on relationships to the ocean, particularly the tides.

The seashore's lowest zone is underwater at all times, even during low tide. This lower zone is also called the sublittoral zone. It is a marine environment.

The intertidal zone (also called the middle, or the littoral, zone) is covered during high tide and exposed during low tide. This is the harshest of all seashore environments, since any animal or plant that lives here must be able to tolerate being submerged for part of the day and exposed to the air and Sun for the rest.

The upper zone, which is never underwater, may be frequently sprayed by breaking waves. It is often referred to as the "splash" or supralittoral zone. Conditions here are very similar to other dry-land areas.

In the Path of the Great Waves