The Maldives consists of approximately 1,190 coral islands grouped in a double chain of 26 atolls, along the north-south direction, spread over roughly 90,000 square kilometers, making this one of the most disparate countries in the world. The atolls are composed of live coral reefs and sand bars, situated atop a submarine ridge 960 kilometers long that rises abruptly from the depths of the Indian Ocean and runs from north to south. Only near the southern end of this natural coral barricade do two open passages permit safe ship navigation from one side of the Indian Ocean to the other through the territorial waters of Maldives.