Deco Habitat Design

[huxley]

but what if they have to attach it to the wall?

"superglue"

[FW]

I would attach the platform with 4 individual chains to the wall, lets say 30' below the platform with individual length chains so the platform would be leveled. Picture mountaineering if they hang a platform off a cliff on a single anchor point in the wall, now turn this picture around and you have the floating platform. My biggest concern would be to pull one of the boulders out of the side wall of the quarry. keep in mind you are applying a couple 1000's pound of force, that might loosen something up and now what, you either go up or that whole thing goes down if the boulder is big enough that you are attached to. It depends on the local conditions but sounds like it is safer to look for the big on on the ground and use it as a counter weight, its not going anywhere neither down or up unless it is too small.
If chain wraps around the rock are done right so that they can only tighten up ( lets say couple loops at the corners of the rock that get combined to a single attachment point for the up chain) this should be foul proof. Just keep in mind the rock might move a little while you fill up the habitat.
Second bet would be drill holes and use expansion bolts, but make sure you have plenty, while the bolt might hold couple thousand pounds the rock might not.

That should work, but I think Mike is right, ropes are easier to adjust.

[Dive Africa]

I am currently thinking the best method might be a combination of heavy duty ratchet straps and chains. I.e use the ratchet traps to adjust the length and ones you are satisfied, then fix length of chain and then remove the ratchet strap, but we'll see.