Peppersauce Cave in southern Arizona is relatively well known but not a tourist attraction. It's in a wilderness area on the north side of Mt. Lemon in the Santa Catalina mountains north of Tucson.
Crystal clear waters, rugged caves and underwater caverns are just a taste of what Bruce Peninsula National park has to offer.
Spelunking is very different from simply walking through a spacious cavern. My experience involved crawling on hands and knees through underground tunnels, and I describe it in this article.