(Photo: minniemouseaunt)
Near the town of St. Martins on the southern coast of New Brunswick, Canada, is a group of caves eroded by the sea. The waters of the Bay of Fundy have among the highest tidal ranges in the world. The force of those waves has cut deeply into the sandstone shore, producing deep caves.
When the tide is low, tourists often explore them. The retreating waters leave fresh finds for them to examine. Just get out before the tide comes in.
(Photo: Jamie in Bytown)
(Photo: Jamie in Bytown)
and the Bay of Fundy itself is home to some of (if not THE) highest tides in the world, which causes a really cool tidal bore. You can even go rafting on it!