The island rises to about from the surrounding sea and covers at high tide, whereas at low tide it expands to due to the tidal range of , second only to the Bay of Fundy in Eastern Canada. There are many caves on the island, and pot holes up to deep in the surrounding sea bed that are believed to be the remnants of collapsed cave systems. The caves on the islands cliffs are at two different levels: the caves in the current inter-tidal zone which are below the water table and are producing stalactites, and many others high up on the cliffs that were on the water line many thousands of years ago.