I took the intro class at CN a couple years ago - as far as I know, the format is the same at all the resorts. The course is free, and the equipment is provided for you. It is designed for people with little or no diving experience. You will start with some classroom materials and a brief swim test - basically just a couple laps in the pool. After that, you will spend some time in the pool with the actual scuba gear on, learning some basic skills. Then, you're off on your first dive! This is included with the course. IIRC, you can go on additional dives for a fee, although these are no charge if you have your PADI cert. Not 100% sure about this, but that's what I seem to recall.
CN 2011, CSA 2012, CSA 2013 (although not soon enough!)