There are four main types of waves in the Philippines: reef, point, beach break, and river mouth. Reef waves are generated by the coral reefs that line the coast of many of the islands. Point waves are created when swells hit a promontory or headland, such as Cloud 9 in Siargao. Beach break waves are created when the swell hits the shoreline directly, such as in Baler. Finally, river mouth waves form where rivers meet the sea, such as in San Juan.