The advantage of walking at low tide

Is that exciting things are uncovered - like this rock covered with mussels, which must be under the sea about half the time. This is at Portreath beach, which I had never visited before. Also huge caves and arches are exposed, great for exploring.  I’d looked up the tide timetable so was confident I was safe. 
After about an hour here I went along the coast about 2 miles to Porthtowan Beach, which is miles long ( and therefore good for my Cancer Research 100 miles). From there I could see Wheal Coates in the distance, so it all joins up.