The three types of coral flats in the Martinican maritime area extend over a length of 43 miles (70 km) and cover an area of approximately 122 square miles (197 km²). The richest in fauna and flora are the fringing reefs of the southern part of the island, between the Rocher du Diamant and the Salines. The most developed are the barrier reefs that border the eastern fringe of Martinique over 15 miles (25 km) and individualize lagoons 1.8 to 5 miles (3 to 8 km) wide. Apart from these reefs are reef formations of non-bioconstructive algal origin. They mainly occupy the steep and rocky shores of the Caribbean coast of the island from a depth of 33 ft (10 m).