The most important aspect is of course your safety. Where you plan to dive is an important consideration to understand when you should think about taking a camera with you. Warm caribbean waters with sand in 30 ft and no current? Go for it. Take a good buddy with you and have fun. Really not much different that shooting in a pool. You have practised a few hours with your rig in a pool, right? As the complexity in your planned dives go up so would my recommendation for additional practise time before worrying about a camera. Current, cold water, low visibility, all make it more difficult to dive safely with a camera. It's also easy for new photographers to get so locked into taking pictures they forget about simple things like how much air they have and where their buddy is.
The other critical consideration is the safety of the reef, some new divers initially have trouble with their bouyancy. Carrying a camera just makes it that much tougher to control your position in the water. The tendency is for new photographers to bounce off the reef a few times before they get the experience. It's extremely painful to watch and no damage to the reef is ever acceptable due to our lack of skills.
Welcome to the amazing world of underwater photography, you are asking the right questions. Be sure and reseach any questions you have here on previous Wetpixel threads and be sure to ask any questions you don't see or don't quite understand.