Which statement best describes the intertidal zone?

• A. The area that is always above water
• B. The area that is always underwater
• C. The area that is below the cliff face
• D. The area that is above water at low tide and under water at high tide

Answer: (D)

The intertidal zone is the part of the coastline that is alternately exposed to air and covered by seawater as tides come in and go out. This means it is above water at low tide and underwater at high tide. Organisms living here have to cope with changing conditions—being wet and dry, shifting salinity, and strong wave action—so they’re often specially adapted to survive both when the area is exposed and when it’s submerged. It isn’t always above water, and it isn’t always underwater, and it isn’t defined by being below a cliff face. So the description that fits best is the one where the area is above water at low tide and under water at high tide.