Sitting just west of Little House, Big House was named for a large house on the shoreline that captains used to anchor in the correct position before the installation of mooring balls. Like many of its sister sites in Half Moon Bay, Big House offers an underwater playground of rocky canyons and ridges with tunnels and archways between them. The site also provides deeper sandy areas and tall ridges heading into the deep — some of these narrow ridges have a build-up of sand on one side but not the other due to prevailing currents, a fascinating natural engineering detail.

Hogfish are a common sighting in the sandy areas, using their long snouts to dig around in the sand for food, with three unusually long protrusions trailing from behind their heads. A Bar Jack often shadows them — interestingly, Bar Jacks turn from their usual silver color to black when following another animal, a striking and poorly understood behavioral adaptation. Big House delivers the trademark Half Moon Bay experience of rewarding, intricate reef exploration in a compact and accessible site.