You should check out this site:
http://www.kayakdiving.com/ They do a really good job of covering kayak diving. I have an Ocean Kayak "Scupper Pro" and dive N. Cal. It works fine for me. I owned an Ocean Kayak "Scrambler" prior to this and it was better in the surf, but it was slower and couldn't carry as much gear. My wife uses a Necky "Dolphin" and is happy with it. I don't like the size of the hatches on her boat.
YOU should ABSOLUTELY paddle various boats before deciding as much really is personal preference.
