Qualifications
Everyone has to know what they're doing in their jobs, but commercial divers really need to know what they're doing. Just because you don't need to go the traditional college route for this career, it doesn't mean you're getting out of some specialized training.
All commercial divers need certification, which can cost anywhere from $8,000 for a two-month program to $20,000 for more extensive training (source). Both of these options will earn you that little slip of paper, but only the latter will prepare you for a wide variety of job types.
Once you're ready, you're going to start as a tender, the lowest level of diver. During this time you'll be working, but you'll continue to earn additional qualifications based on time on job sites and time underwater. No matter what you want to do as a commercial diver, you can pretty much expect to need a piece of paper saying you can do it. We suggest a nice (waterproof) binder to keep track of it all.