Replying to Scuba Diving?

Long story short I am going to Belie in early September and I figure I need to learn to Scuba Dive before then. I've always been interested, but never really have been urged to pull the trigger on training until now. I have a strong swimming/water background (4 yr state swimmer/instructor/lifeguard) so i'm pretty comfortable in the water.

What I'm looking to hear from you guys is how much certification do I need to dive in some sweet places in Belize. There are a couple PADI certified training centers around me, with a bunch of different certifications and I am trying to figure out how much training I need! Also wondering if there is any specific places in Belize for diving that people would recommend.

Thanks, +K to all/