So, there are basically 4 types of diving.
The first and most basic is recreational diving, which you are familiar with.
Another is scientific diving. Scientific diving is exempted from Commercial diving, although most research divers are paid, and may use tools, they use tools for their research and diving is ancillary to their real job. Research may be conducted by NOAA, Universities, National Park Service, or myriads of other organizations, or by aquariums. If you are doing research or scientific diving, you are doing so under the auspices of a Scientific diving manual, which are often written and used by members of AAUS, or the American Academy of Underwater Science. Manuals do not have to be approved by AAUS, my former manual was not, but was written following their guidelines.
Third is Commercial diving. I can't speak about commercial diving, as I know just enough to make a fool of myself.
And fourth is military diving.
I think you are interested in scientific diving. Typically scientific divers are graduate students at a university that has a marine biology or underwater archeology program. There are very few opportunities for undergrads to do any scientific diving. FSU or UF has such a program, I know nothing about it, University of Western Florida has an excellent underwater Archeology program for undergrads.