A team of cave divers have been exploring an underwater cave at Rick's Spring in Utah. Located on US Forest Service land in Logan Canyon, the limestone cavern has been explored these last three years. Though entry is through diving, sections of the cave are air-filled, including a chamber with a large waterfall. Approximately 2,500 feet of cave passage has been explored to date.
The Cave Diver's Forum includes interesting cave and trip descriptions, along with photographs: http://www.cavediver.net/forum/showthread.php?t=11223
