Tide pools are actually rock depressions filled with seawater when the tide goes out. The reason tide pools are fun to investigate , especially for children is that they can be filled with sea life left behind by the tide. There are also small sea creatures that can endure the extreme temperature changes from the sun that heats the shallow pools formed in the rocks.
When ever I am over on the cliffs of our shore line, I make my way down to sea level and look through the thousands of little tide polls and see what the sea has delivered. You have to get down real close and study the water and soon you will discover the many little sea animals and plant life that will fascinate you.
Here is a photo from a recent outing and you can see clearly all the tide pools as they are formed in the rock ledge that gets completely covered with water at high tide. That is when to go looking to find your own little miracles of the sea.
In another area, the tide pools can look like this photo below. This sea bird was actually drinking sea water and getting his vitamins and nutrients at the same time with the small sealife washed into the tide pools.