NCL used to offer a program called Dive-In. It was great. You were the first ones off of the ship and did some great dives. I'll check their website to see if I can find that. What ports will you be visiting?
They still do the program, we really enjoyed it on the 3 cruises we did with them. Check out their website: http://www.ncl.com/shorex/dive_in.htm. I didn't have time to search around for too much information, but we found the program to be well worth the money.