San Juan County Park

San Juan County Park sits at Smallpox Bay on the west side of San Juan Island, about 10 miles from Friday Harbor along West Side Road. Divers enter from the sandy park beach, generally the most convenient shore launch on the island. The bay's bottom is sand and eelgrass to about 20 feet, and boulders begin near that same depth. Along the north side, the substrate steepens into a boulder wall with ledges and caves down to roughly 50 feet, while bull kelp grows along the perimeter of the cove just outside the sheltered water.

The park's name traces to a difficult episode in local history. Coastal First Peoples reportedly waded into the cold spring water at this cove to break fever during 19th-century smallpox epidemics, and the name carried over to the modern park. That oral tradition is the site's dominant historical story.

Three biomes meet at Smallpox Bay. Eelgrass across the sandy bottom of the inner cove marks the sheltered water as a seagrass biome. The kelp forest biome begins at the perimeter, where bull kelp fringes the cove just outside the sheltered water. Past the kelp on the north side, the boulder wall, its ledges and its resident lingcod put the outer edge of the dive squarely in a rocky reef biome. The site works for both scuba and snorkeling, with the shallow inner bay accessible to beginners and the outer wall reached by intermediate divers. The outer boulder area and kelp edge see moving water from Haro Strait; slack water is recommended for depth work. Vessel traffic in Haro Strait is a surface hazard for divers outside the cove.

The county day-use lot inside the park has flush toilets, drinking water, a picnic shelter, and a small boat launch; day use is free, and overnight vehicle parking for kayakers and boaters runs $20 per night. The park has 20 campsites reservable through the county. Marine Area 7 rules govern the water: rockfish retention is prohibited across Marine Areas 6 through 13, lingcod spearfishing runs May 21 to June 15 with a 36-inch maximum and a daily limit of 1 fish, and cabezon is open May 1 to November 30 at an 18-inch minimum with the same daily limit. WDFW enforces.