AllMovie

The critical role played by coral reefs is explored in this episode of the series, narrated by Ted Danson. Tiny creatures are responsible for building the structures that reach hundreds of miles in length, offering food and shelter to a vast number of sea animals. Fish, mollusks, crabs, eels, and sponges are just a few of the organisms that depend on reefs for survival. Challenge of the Seas, Vol. 6: Cities in the Sea discusses the many factors that threaten the survival of coral reefs, including pollution and the destruction of reefs by recreational divers.