The nurse sharks and stingrays are at Shark Ray Alley in the Hol Chan Marine Santuary. This is a shallow dive with I think a max depth of 30' and in some places only 6 or 8 feet deep (lots of snorkler's)It's also the only place I know of for a nite dive.It's a channel, so depending on the tide you will have some current either going out or coming in.I'ts worth doing IMHO. Oh, the Park charges a small fee so be sure and ask you dive operator how much so you can bring cash with you. I think It's 5 bucks US p.p.
The reef is about 500 yards off shore so no shore diving. Inside the reef depth are something like 50' - 80' outside 80'-120'. Lots of nice sand chutes, swim througs,coral and fish.I'll look in my dive log and tell you what our favorites have been. For wall diving you have to go to the outer atolls, and this requires a full day for three tanks.
My favorite so far is Half Moon Wall.I'm not sure if anyone goes there without the first tank being the Blue Hole.
Do you have three days to dive (using the 24hrs. befor flying rule) or threen days on AC. Hope this helps. I'll look at my log book and post our favs.