The distinction between barrier reefs andfringing reefs is sometimes unclear becausethe two types grade into one another. Likefringing reefs, barrier reefs lie along thecoast, but barrier reefs occur considerably farther from shore, occasionally as far as100 km (60 mi) or more. Barrier reefs areseparated from the shore—which may alsohave a fringing reef—by a relatively deep lagoon(Fig. 14.17). Largely protectedfrom waves and currents, the lagoon usu-ally has a soft sediment bottom. Inside thelagoon, coral formations variously knownaspatch reefs, coral knolls,orpinnaclesdepending upon their size and shape may grow up nearly to the surface.