Robert Gavilan is a former CIA agent.
I would normally have addressed him as a oceanographic trouble-shooter, as he sometimes implies, but that designation really does not tell much about what he does and would likely be argued by his boss at the Oceanographic Institute, Marion Jaworski. Truthfully just about anything he might say would be probably challenged by her since she seems to spend most of their little time together fussing about one thing or another regarding him.
Yet another reason for promoting his once Agency ties is the fact that on numerous occasions, he is approached by this old associate or that one for one little job to be done. Either Jaworski is a whole lot more lenient in his 'side-trips' than she lets on or the Agency must be providing financial incentives (purely my supposition) because despite his grousing about them, he goes off on these excursions easily enough.
When he is not returning to his old roots, the work at the Institute that Gavilan takes part in is, despite what his boss might say, is that largely of a trouble-shooter in that whenever there is anything at all out of the ordinary (i.e., non-research related) he is the one to get the call. He shows himself to be quite good at such matters as well as being an expert in underwater activities.
He also teaches a college-level class at the Institute and being a very good looking, physically fit bachelor around 25 years old, he is extremely popular with the young female members who invariably fill his lectures. From what we see of him, though, he is very friendly with them and appreciative of their attention but not enough to partake of their obvious offers.
Sharing his home, for reasons that even he would be hard pressed to explain, is Milo Bentley, an old friend of Gavilan's father who showed up needed temporary lodging and never left. Bently is a conman at heart and frequently getting into trouble but he has some good feelings towards Gavilan and does, a time or two, try to help out with this or that. Luckily Gavilan is good enough at his work to survive this assistance.