The islands lie on a limestone platform in several sections with carbonate banks. The largest is the Great Bahama Bank with Andros Island, while smaller ones form a chain extending from the Straits of Florida to the Caicos Islands. The total area of the banks is nearly 260,000km², much greater than the 1,300 islands (12,000km²). The islands are low-lying and mostly very porous limestone so there is no surface water. Therefore the corals can grow close to the shore. Coral reefs occur mostly fringing the bank margins, with some small patch reefs on the bank in areas with high tidal circulation, and a few bank-barrier reefs. The most important reef regions, with their approximate areas are, from the North: Little Bahama Bank (323km²), Bimini (90km²), Berry Islands/Andros (182km²), New Providence (30km²), Eleuthera/Cat islands (200km²), San Salvador/Rum Cay and Conception Islands (132km²), Exuma Cays/Ragged Islands (386km²) Samana Cays (50km²), Plana Cays (31km²), Mayaguana (72km²), the Inaguas (164km²), Hogsty Reef (23km²), Cay Sal Bank (153km²) and Crooked/Acklin Islands (151km²).

The Bahamas with a total surface area of 13,880 km², comprise 13 major islands and 700 smaller islands and cays on 2 large, shallow banks. The islands are aligned northwest to southeast covering more than 1,400 km from near Florida to southeast Cuba. The area covered is approximately the distance between Puerto Rico and Trinidad and Tobago. Coral reefs fringe most of the north and east windward coasts and bank edges.

The Bahamas contain 13 major islands and more than 2000 smaller islands or cays, distributed over 260,000 km² on 2 large, shallow banks (Great Bahama Bank and Little Bahama Bank) separated by depths exceeding 4000 m. They are aligned northwest to southeast for more than 1400 km, from near Florida almost to Haiti. Coral reefs fringe most of the north and east windward coasts and bank edges and cover 1832 km2 of the Great Bahama Bank and 324 km² of the Little Bahama Bank. Andros Island is the largest island with the third longest barrier reef system in the world (229 km). Reef development in the Bahamas is limited by hurricanes in exposed regions, cold winters in the northern Bahamas and by turbid, hypersaline waters on the leeward bank margins.

Bermuda is an isolated island chain 920 km off the coast of North Carolina on the Bermuda Platform. Together with the Challenger and Argus Banks, they occupy about 900 km². The fringing, bank-barrier and lagoonal patch reefs form the most northerly coral reef system in the Atlantic and are supported by warm water eddies from the nearby Gulf Stream. Coral diversity is, however, limited by cool winters.

The 13 major islands and 700 smaller islands and cays lie on a limestone platform covering 13 880 km² area comprised of two large, shallow carbonate banks. The largest is the Great Bahama Bank with Andros Island while the smaller forms a chain extending from the Straits of Florida to the Caicos Islands. The islands are low-lying and comprised mostly of very porous limestone so there is no surface water and therefore corals can grow close to the shore. Coral reefs occur mostly fringing the bank margins, with some small patch reefs on the banks in areas with high tidal circulation and with a few bank barrier reefs.