Dirk Pitt is an agent with N.U.M.A.
Truthfully, he is an employee, not an agent and N.U.M.A., the National Underwater and Marine Agency, is not an Intelligence bureau but one dedicated to maritime exploration and discovery. The adventures he gets into, and the huge consequences that result in his help, make this series belong firmly in this compendium.
With the exception of James Bond and possibly the Man From U.N.C.L.E., there is no member of this collection of spy heroes about whom more is known than Dirk Pitt. First, the number of web-sites existing is amazing, each with its own slant on the character. And second, the author was good enough to write a separate volume about his hit hero and himself.
Pitt stands over 6'3, weighs 180 lbs and has green eyes and wavy, black hair. Born in November, 1952, in Newport Beach, California, the son of a U.S. Senator, he attended the U.S. Air Force Academy from which he graduated in the early 70's. During his military service, from which he retired with the rank of Major, he was awarded numerous medals such as the Distinguished Flying Cross with two clusters, a Silver Star, a Purple Heart, and several other commendations.
His interest in the Titanic and his love of the ocean sparked his movement to work with NUMA, an organization dedicated to the preservation of the world's marine environment. He is able to afford his continued love of exploration, as well as a fascination with vintage cars, thanks to a large inheritance from his grandfather.
As the series progresses, the character actually ages, though he does not lose his ability to hold his own against anyone. Eventually, however, a co-starring role is given to his grown children which breathed new life in a series that was nowhere near done.
Interestingly, the author, Clive Cussler, passed the principle writing to his son, Dirk Cussler, from whom the character originally got his name.
Note: The third adventure, "Raise The Titanic", was turned into a movie in 1980 starring David Selby, Richard Jordan, and Jason Robards. It was a solid movie with good effects, especially when the ship breaks the surface. Still, the character of Pitt, played by Jordan, was, IMHO, far too subordinate to one Selby had since Selby was by far the bigger star at the time.