Daylonious:
Eden Rocks or Divetech (is it the Turtle Reef location I want?) looks like good decisions.. maybe a two tanker and Divetech and a quick tank at Eden rocks then back to the ship..
D.
That should work, it's about 20-25 mins. to Turtle Reef - which is where you want. There'll be cabs waiting right at the dock. Most of them are mini-vans so it's convenient if you're bringing your own gear.
The mini-wall there is better than Divetech/Cobalt Coast. If you want to get out to the North Wall fast from Turtle Reef, they rent Apollo scooters for around $40 to anybody - no training required.
I'd go out deep to the North Wall first, then on your second dive go along the mini-wall, it gets to about 65' in places - mostly about 35-40'. But there's a lot of interesting stuff down the wall. Tarpon in the shadows and look up occasionally for Turtles, they escape from the farm just to the south - beats becoming a souvenir...
Back at Eden Rock, head out toward the Grotto, it's a little more interesting - some swimthroughs and short overheads. You'll see your ship anchored out in front of you. It's a short walk back to the embarkation pier from there - everybody is tendered in on Cayman. There's lockers and stuff there, but we just left our bags on the table, no one messed with anything all week on Cayman.
It's going to be really disappointing after Turtle Beach though. The coral's been ground down by thousands of divers and there's junk in the water - tires, concrete, things fallen off the cruise ships. Also not much past 40' - we seemed to hit a line past which it seemed like it was just flat sand. And I don't think you'd want to swim out under the ships, the others are probably leaving closer to 5PM. Georgetown shuts down around 6 or when the last ship sails. When we were at Eden Rock around 3pm, we were the only two there, most of the cruise ships - and their business - had left. I wrote in my log that it was the most disappointing dive all week.
Personally I'd do the third dive at Sunset House, it's all divers, so you should be able to find a buddy if desired. And it's 2-3 mins. back to the port via Taxi - just over a mile walk or so(not sure about this distance).