This bathymetric map of the San Juan Islands shows the depth of the water throughout the islands, as well as the geology of the islands.
Originally published within "Geology and Seafloor Bathymetry of the San Juan Islands" produced by Greene, H.G,. Dieter, B., Endris, C. Lopez, H., Murai, L., and Erdey, M. of the Center for Habitat Studies, Moss Landing Marine Laboratories.
You can download the entire 11.7MB file using the link above.