Alacranes is a National Park and Mexico's only Barrier Reef Tract. It is situated in the middle of the Campeche Bank some 100 km from shore and remains relatively protected from human activities. The reef itself has a breakwater reef rimming the eastern windward side and sandy shoals, islands and patch reefs rimming the west. The deeper central lagoon is filled with reefs that form the best example of a 'reticulate' reef anywhere in the World. 

Other types of Dispersed reefs occur in less protected settings, such as these Granular Reefs off Eleuthera Island, in the Bahamas. These form over flat shelves and dampen wave activity via diffraction. This dampening is so efficient that they trap sand and develop a lagoon just like traditional linear reefs. But the absence of a clear breakwater means these reefs pose a serious hazard to navigation.

This is a typical linear fringing reef at Punta Maroma with a wide reef-front and back-reef separated by a reef crest. The crest forms the highest point and adjacent zones slope away from it. This crest breaks incoming fairweather waves and produces a narrow breaker zone which can be used to delineate the crestline. This line of breakers generates currents that flow across the back-reef and into the lagoon without producing a wave-set up.

By contrast, the Fringing reef at Mahahual has an intertidal reef flat instead of a crest and a back reef. It is so flat that, at low tide, you can walk across it in ankle-deep water (although we wouldn't recommend this as a popular activity for obvious reasons).  This flat breaks incoming waves and, as they propagate over the flat, their energy is significantly reduced. The flat then restricts circulation in the lagoon and produces a wave set-up during periods of high wave activity.

Barrier reefs are few and far between, but Belize is full of them. They typically have steep reef fronts and deep lagoons but show other more significant differences from fringing reefs. In the reef-front, for example they lack the typical rocky terrace and are composed of an extensive and high relief spur-and-groove zone which extends almost to the shelf-edge in many places. Interestingly, this system of spurs consists of several spur 'sets' which decrease in frequency downslope, as can be seen opposite.

Reefs with well-formed reef flats are rare in most of the Caribbean but Panama is their Shangri-La. Not only are they the only reef type to form there, but are similar in many ways to their classic counterparts in the Indo-Pacific,  and include terraced algal ridges, hoa (spillways) and motu (islands). Why Panama I hear you asking? Good question. It may have something to do with the lack of hurricanes or maybe even the effect of the Caribbean Low-Level Jet on the wave field. Hopefully we'll know soon.