Who is Dirk Pitt from Raise the Titanic! and what is their importance?

Dirk Pitt is the main character and hero of the novel. He is a scientist for NUMA and is the Special Projects Director. Pitt is also the son of a powerful Senator. Dirk is the man who went ashore at Novaya Zemlya to rescue Sid Koplin when he didn't show up at the rendezvous. He shot the Russian guard and the dog, destroyed Koplin's sloop and brought the injured man to safety.