Many of the most awe-inspiring caves formed along the shores of oceans and lakes. Also known as littoral caves, these geological wonders are carved into rocky coastal cliffs through long-term wave action along weakened fault lines in cliffs.
In addition to spelunking, sea caves provide ample recreational opportunities for kayaking, swimming, free diving, scuba diving and more. While many of these caves are found in the craggy coastlines of Europe, some of the largest sea caves in the world — such as California's Painted Cave and Oregon's Sea Lion Cave — can be found on the rocky Pacific coast of the United States.
Here are just 9 of these extraordinary watery wonders.