What Is the Shoreline Zone That Alternates Between Exposed and Submerged?

It’s called the intertidal zone (or littoral zone / foreshore / seashore).

• Boundaries: Between the highest high tide (strandline) and lowest low tide (chart datum).
• Conditions: Alternating immersion (marine) and exposure (terrestrial) – temperature swings, desiccation, wave shock, salinity shifts.
• Life: Specialized organisms—barnacles, mussels, sea stars, anemones, crabs, algae—zoned by tolerance to exposure time.

This dynamic ecotone is one of the most biologically productive and physically stressful habitats on Earth.