Mr. Cussler also connected with readers by turning his love for scuba diving into an oceanic lifestyle that paralleled and validated his superhero.

He first created the National Underwater and Marine Agency as a fictional government organization that employed his hero in the Dirk Pitt books. Then, in 1979, he founded an actual National Underwater and Marine Agency as a private nonprofit group committed to “preserving maritime heritage through the discovery, archaeological survey and conservation of shipwreck artifacts.” It underwrote his maritime ventures.

With Mr. Cussler leading expeditions and joining dives, the organization eventually located some 60 wrecks. Among them were the Cunard steamship Carpathia, first to reach survivors of the lost Titanic on April 15, 1912, then itself sunk by German torpedoes off Ireland in 1918; Commodore Cornelius Vanderbilt’s coastal steamer Lexington, which caught fire and went down in Long Island Sound in 1840; and Manassas, the Confederacy’s first Civil War ironclad, sunk in battle in the Lower Mississippi in 1862.

His first nonfiction book, “The Sea Hunters” (1996, with Craig Dirgo), was an account of his NUMA exploits, some of which were portrayed in television documentaries featuring Mr. Cussler as narrator. Valuable artifacts raised by his expeditions were given to museums or governments.

Mr. Cussler, who named his franchise hero after his son Dirk, acknowledged that Dirk Pitt’s character was his own alter ego. His later novels, many co-written by his son or others, often included himself as a character who saves the day. His son, a daughter and friends were also used as characters in his books.

“I’ve been doing Dirk Pitt for 30 years,” Mr. Cussler told The Times in 2000. “Maybe I can find another writer down the line to take him over. It’s not the money; it’s the fans.

“I’d like to retire,” he continued. “I’m toying with the idea of Pitt having a son who shows up. He’s getting a little long in the tooth. When we started out, we were both 36 years old. Now he’s a little over 40, and I’m pushing 70.”