Bonneville Seabase, in Grantsville, Utah, taps thermal water at 40°C in an open-air pool. The site, unusual for the region, offers open-air bathing near the Great Salt Lake.
Insider tip — Bonneville Seabase is a landlocked scuba diving and thermal spring site fed by ancient seawater from the Bonneville Salt Flats basin, making it one of the most unusual thermal experiences in the American West. The spring-fed pools maintain a consistent year-round temperature amid the barren salt desert landscape. Divers come for tropical-temperature dives far from any ocean. The surreal juxtaposition of warm clear water and surrounding salt flats is unforgettable.