Barbados is a coral island, pushed out of sea by volcanic activity millions of years ago. Most of the country is circled by coral reefs with its stunning underwater world which fall in a series of "terraces" in the west and go into an incline in the east. The north shore of the island is lined with jagged coral cliffs which collide with the relentless breakers. Within the Barbados coral core there are many caves and underground lakes which provide an excellent supply of drinking water.