The Rock at Two Tides

The heading is “Up and Down.” Ocean water does not stay at one level. Its slow rise and fall is called a tide.

At low tide, the water is lower. More sand is bare. At high tide, the water is higher. Water covers more sand.

It can be hard to see this slow change. Look at a big rock on this beach. At low tide, its base is dry. Hours later, high tide may cover its base.

A picture shows the same rock at both tides. The caption says, “Low tide, high tide.” The rock stays in place. The water moves up and down.