intertidal

of or denoting the area of a seashore which is covered at high tide and uncovered at low tide.

About 950 species of Sea Urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to 5,000 meters.

intertidally

Between tides, at low tide and high tide, but not at either - intertidally. Between low tide and high tide. The tide is on the way to low tide going down but not quite all the way down to low tide. The tide is on the way to high tide and is not quite high tide yet. The tide is intertidally.

I am going to run on the beach intertidally. Instead of saying I'm going to run on the beach at high tide or low tide. I am going to run on the beach intertidally to low tide.. The shells were getting exposed intertidally while it was approaching low tide. The beach was becoming more narrow to the rocks on the cliffs intertidally while it was approaching high tide.