Thank you for the positive feedback! I hadn't been to the GOM board, before.
The sticky meshes are fixed, though I'm not sure why they were sticky. I made their bounds boxes, rather than triangle meshes. My guess is that the meshes are so shallow that collision detection is confused. I notice that the shallow meshes' rendering gets hosed if the avatar gets too far away from them. This effect is hidden by the mist, fortunately.
Getting transparency to work properly was a chore. I manually adjusted rendering order with parenting and deparenting. Additionally, the waterfalls have pass index 1, everything else has 0. This gives the correct transparency, but kills two-sided meshes, which I'll replace later on.
I made the lake and waterfall materials Z-buffered. This prevents them from occluding the transparent avatar. In Ahnonay, by contrast, the transparent avatar is occluded by the water when in the water. Is that occlusion desirable? I think The Transparent Avatar will be my new cavern name.
Adjusting rendering order makes the waterfalls show up transparent in Blender, which is nice.
I will add more pagodas. The rule is that they must be constructable with the Eames House of Cards. I see on the Eames Office web page that the Giant House of Cards is now available, but the Paper Pagodas are bigger!
I quite like the combination of cards and waterfalls.