These are the most northerly coral reefs in the Atlantic and survive because of warm-water eddies from the nearby Gulf Stream. Cool winters are probably responsible for the low diversity of stony corals (only 20 species, with Acroporanotably absent). Nonetheless, the reefs are well developed on the Bermuda platform in an atoll-like form (750km²), with patch reefs in the central lagoon.

This is an isolated island chain and the most northerly coral reef system in the Atlantic. The islands and reefs surround a central shallow lagoon, which contains a complex of shallow, highly diverse patch reefs interspersed with seagrass beds and isolated pockets of mangroves.

The Bermuda islands are a 53 km² chain of aeolian limestone islands in the North Atlantic at 32°N, 1050 km off the coast of USA and 1660 km north-east of Florida. The 7 main islands are connected by bridges and have a maximum elevation of 79 m. The climate is sub-tropical and sea surface temperatures range from 16°-30°C. Bermuda’s reefs are geographically isolated; there is no land with reef corals nearer to Bermuda than the Bahamas, 1350 km to the southwest. These are the most northerly reefs in the Atlantic and amongst the most northerly in the world. The Bermuda platform of about 990 km² (maximum 200 m depth) has an atoll-like reef tract, unique in the Caribbean, and includes patch and terrace reefs covering 550 km². Bermuda has about 22 species of hard corals, but branching Acropora species have never been recorded in Bermuda. The shallow outer lagoon, rim and fore-reefs are dominated by massive high relief species such as Diploria strigosa and D. labyrinthiformis, Montastraea franksi, M. cavernosa and Porites astreoides. Nearshore reefs and deep fore-reef habitats are dominated by branching Madracis decactis, Madracis auretenra and Oculina species.