Stellwagen Bank and Cashes Ledge are two highly productive undersea islands within the Gulf of Maine. Covered with a layer of sand and gravel, their bedrock resisted glacial scouring that eroded and deepened adjacent basins. Probably nowhere in the Gulf are so many different habitats in such proximity as in the Stellwagen Bank National Marine Sanctuary. From hardy anemone-like cerianthids nestled in the muddy sands along its flanks to juvenile cod hiding among its boulder fields, Stellwagen Bank and nearby Jeffreys Ledge exemplify marine biodiversity in northern waters. The multitudes of sand lance and herring on and around these undersea islands attract groundfish, bluefin tuna and the mighty whales, making the Sanctuary one of the top whalewatching spots in the world. Cashes Ledge is a mountain within the Gulf whose summit is capped by a unique kelp bed and whose clear waters support one of the deepest cold-water seaweed communities in the world. Its fields of anemones and varied sponge communities pro duce a singularly colorful and fascinating marine landscape.