The islands of the Maldives are part of 26 natural coral atolls. The word ‘atoll’ is originally a Maldivian word which found its way into other languages. The atolls are underwater platforms lying on a ridge in the Indian Ocean. The edges of these platforms are higher and form a large protective ringrif with occasional openings. In the atolls islands are often surrounded by lagoons and have their own protective reefs and lagunes.