the cheryl and philip willstein family. bernard and irene schwartz. roslyn p. walter.porate funding is provided by mutual of america. designing customized, individual and group retirement products. we're your retirement company. additional support is provided by -- the corporation for public broadcasting. and by contributions to your pbs station from viewers like you. thank you. >> narrator: on the entire west coast of the americas, there is no other estuary like san francisco bay. immense in size, covering over 1,600 square miles, it is one of the great estuaries of the world. >> estuaries are the part of the planet where land and sea come together. it's magic in a lot of ways. >> narrator: it was an estuary of breathtaking abundance, a marvel of nature. >> so on a per acre basis, this is more productive than the rain forest, more productive than the redwood forest, more productive than coral reefs. these are the most biologically productive regions on earth. >> narrator: next on "saving the bay." >>> underwriting support for "saving the bay" comes from the bay area t