If you are interested in underwater photography, I first recommend that you complete PADI (Professional Association of Diving Instructors) courses to a minimum of the Advanced Open Water Diver level. This will give you the basic skills you need to be able to dive and control your buoyancy, which are the basic requirement for underwater photography.
As part of the Advance Open Water Diver courses you can do the following:
Digital Underwater Photography
Underwater Photography