The Caribbean is a region consisting of the Caribbean Sea, its islands, and the surrounding coasts. Situated largely on the Caribbean Plate, the region comprises more than 7,000 islands, islets, reefs, and cays. Physiographically, the Caribbean region consists mainly of the Caribbean Sea to north, bordered by the Gulf of Mexico, the Straits of Florida, the Northern Atlantic Ocean which lies to the east and northeast. The geography and climate in the Caribbean region varies. Some islands in the region have relatively flat terrain of non-volcanic origin. The waters of the Caribbean Sea host large, migratory schools of fish, turtles, and coral reef formations.