Many organisms are restricted to a particular geographical area by the surrounding physical environment, for example polar bears are highly adapted to cold, Arctic conditions and would struggle to survive in the deserts of the Sahara and vice versa for lions and tigers. Corals suffer from the same restrictions, they are possibly restricted to local areas, by the surrounding substrate, food supply or intolerance to physical changes in temperature.
Cold-water corals are found in many of the world's oceans, many species attain high densities in areas away from the influence of coastal seawater, preferring an environment with a stable salinity and temperature regime. They occur in a wide range of different depths, but nearly all are found below the depth which light can penetrate, and below the storm wave base which can damage corals. Being a passive suspension feeder, nearly all corals occur in areas with a high speed bottom current flow, bringing food and being strong enough to remove any sediment which may potentially smother the coral.