Don, a guided tour of the dig would probably take an hour or so, depending on how long you want to stand around and watch the sea creatures doing their thing. There's a couple of other areas at Atlantis that are also "aquarium-like" that you can see for free. One is the predator lagoon (entrance is just outside the Coral Lounge (the gazebo looking restaurant on the edge of the large lagoon); and the Cave--near the Beach Tower. You can also watch a lot of the sea creatures in the dig from the Hall of Great Waters in the Royal Tower. Editing to add: If you take the water taxi over from Nassau, you can walk through the Marina Village, past all the huge yachts to the very end. There's a staircase there that leads to the Casino. I never saw anyone asking for key cards or anything there--you just walk in. Go through the casino to the other side and you'll see the promenade in the Royal Tower--if you keep walking you'll see the Hall of Great Waters. The only place I saw people asking for key cards was outside the Dig and between the East and West Towers of the Royal Towers.