Belvedere Lagoon is an artificial lagoon on San Francisco Bay in Belvedere in Marin County, California. Narrow strips of land separate it from Richardson Bay and Raccoon Strait. The lagoon is owned and maintained by the Belvedere Lagoon Property Owners' Association. The lagoon is not accessible by boat from San Francisco Bay, and no pub…Belvedere Lagoon is an artificial lagoon on San Francisco Bay in Belvedere in Marin County, California. Narrow strips of land separate it from Richardson Bay and Raccoon Strait. The lagoon is owned and maintained by the Belvedere Lagoon Property Owners' Association. The lagoon is not accessible by boat from San Francisco Bay, and no public access is provided. Until somewhat late in the 20th century houseboats were present in Belvedere Lagoon.