I may have to post this in two parts, I am actually working today.
My buddy and I dived it with one support person, so we had three people carrying gear for two divers. It sucked. The "1.1 mile hike" does include 700 feet of vertical. Pretty steep trail even without gear. If memory serves the water surface is around 6200 feet elevation, the parking lot is up around 6900, maybe 7000 feet elevation. Obviously an altitude dive.
You have to check in at the ranger station to get a permit to dive. The short version is if you get bent the rangers will try to render what aid they can when they find time in their busy schedules. It was enough of a shock getting lectured before they issued my permit that I looked over my dive plan -again- before I drove up to the parking lot. Nearest chamber is Seattle, about the quickest you could get there from the water is around three hours, assuming the chamber is available and the fast helicopter is available.
Gotta go. No wheeled vehicles on the trail, you carry your gear on your back...
Unlimited vis, it was a cool dive.