The theory's of coral reef formation and origin have not changed significantly since Charles Darwin first proposed them. Although there have been refinements since 1842 Darwin's original concepts are still the foundation of what is currently believed to be coral reef origins. On his voyage aboard the Beagle, Darwin observed 3 kinds of reefs: fringing reef, barrier reef, and atoll.

The western Florida Keys (Big Pine Key to Key West) are believed to be remnants of large coral reefs from the last glaciation cap in North America that reduced the ocean water level, drowning the coral reefs. The eastern Florida Keys (Loe Key and up to Long Key) were patch reefs that became islands.

The recent coral reef formations came about when water temperatures rose and the reefs could grow. The new coral reefs grew on old small coral reef beds that had eroded, thus creating relatively flat reefs (banks), that are not true modern fringing reefs in that there is a substantial lagoon between the shore and the coral reefs. Thus the name Bank/Barrier reef is coined for coral reefs in the Florida area. They differ from barrier reefs in that the lagoons are much shallower and there is a reef flat or bank.