One of the disadvantages of the low wave environment is the problem of increased amounts of silt falling on the corals. These reefs which come in many different shapes and sizes, are surrounded by sand. Branching corals, such as Madracis , Oculina , the fire coral Millepora alcicornis , and soft corals such as the sea rod Pseudoplexaura , flourish in this calmer environment. The rim reefs create a circle along the edge of the lagoon and are formed on the raised rim of the Bermuda platform. They range in depth between 2 and 10 meters.
North Rock is an example of a rim reef area.
Many different hard corals, especially massive boulder corals such as Brain and Star corals are abundant here, as well as sea rods and sea fans such as the large Gorgonia . Th ey are small, generally rounded reefs that extend to the sea surface and have waves continuously breaking over them. This makes the water look as though it is boiling. The picture here was taken while scouting for sites to put the underwater camera seaward of the rim area.