My son did Atlantis at Cozumel and had a great time. However, from diving both places, I'd think the Grand Cayman one would have better views. Plus, there appear (as of 3 weeks ago) to be _two_ Atlantis subs in Grand Cayman.

If you search the net, you can find their web site - as I remember booking thru them saved maybe $10 or $20.

Dana