Thank you Snailmaster, that is a great idea. I began trying to make this happen last night and ran into several issues. The crab hut will have to be made out of plastic considering a thick glass in the correct shape will be to hard to find. Plastic doesn't have any weight, so a rock fortress will have to be built around hut which spoils my plan because you won't be able to see your crab! It would still be useful, but if your crab spends most of his time drying, you will spend most of your time looking at a pile of rocks.
I also had another idea to hold the plastic down. Take 4-6 heavy duty suction cups and attach to container and suction to glass bottom (My girlfriends idea actually but it sounds like it will work). The right suction cup will easily hold it down. I will go to the hardware store this weekend and attempt o rig it up.