"The taller of the two pulled off his hood and ran his hands through a thick mane of ebony hair. His face was darkly tanned, and the eyes were the most vivid green.... He had the look of a man who smiled easily and often, who challenged life and accepted the wins and losses with equal indifference. When he stood at his full height he was three inches over six feet, and the lean, hard body under the dry suit strained at the seams."

This is Dirk Pitt, hero of Raise the Titanic! and six other novels, including the current best-seller Deep Six (Simon & Schuster, $17.95). But the passage could also describe author Clive Cussler, who created Pitt in 1973 as an idealized alter ego. "Pitt is 10 to 15 years younger than I am," admits Cussler, 52. "His eyes are greener, and he has more hair. And Pitt does better with women than I ever did."

The resemblance is more than physical. In Deep Six Pitt searches for a sunken ship that is polluting the ocean with a deadly poison, and he reports back to a federal agency called NUMA. In real life, NUMA (the National Under-water and Marine Agency) is the name of a nonprofit organization founded by Cussler in 1976 to support and supervise underwater exploration. So far Cussler has discovered 34 historical wrecks. Among his finds are two Civil War ships (the Union's Cumberland and the Confederacy's Florida) and Commodore Cornelius Vanderbilt's elegant steamboat, Lexington, which sank in Long Island Sound more than 140 years ago. Cussler never claims salvage rights; when he sends down divers, they are used to confirm identification of the vessels. If artifacts are retrieved, they are donated to museums and universities.

Since May Cussler has been circling the North Sea and the coasts of Scotland, Denmark, Holland and France in search of, among other vessels, the German submarine U 20, which sank the Lusitania in 1915, as well as the Bonhomme Richard, John Paul Jones' ship, which went down off the coast of Yorkshire in 1779 in one of the most famous battles in naval history. On his chartered 63-foot yacht Cussler often spends 12 hours a day monitoring a sonar scanning device that makes ultrasonic sound-wave maps of the seabed. Sunken ships show up as dark clumps on the machine's printout. "A lot of people don't understand why I'm not out diving for treasure," says Cussler, who has spent $55,000 so far on his current expedition. "But I get a high just knowing I've found a ship."

Cussler can afford such thrills, thanks to Dirk Pitt. In the last decade Pitt has earned the author an estimated $5 million, some $500,000 of which he has spent on shipwreck expeditions. But Cussler's writing career began long before that with a weekly cooking column for the Globe Pilot in Costa Mesa, Calif. Using the byline Sally Salamagundi, Cussler offered recipes culled from cookbooks. The feature was a smash, until one day Cussler printed a recipe for oatmeal cookies that left out a vital ingredient. Calls from angry readers jammed the newspaper switchboard. Recalls Cussler, "When they reached me, they heard a masculine voice saying that Sally was on vacation."

It turned out to be permanent. Cussler moved to Hollywood and started working for the D'Arcy advertising firm. He wrote copy for General Tires, Budweiser and Ajax detergent. Over drinks one evening he and a group of friends thought up the memorable Ajax White Knight commercial ("It's stronger than dirt").

At night and on weekends Cussler labored at the typewriter. His first published novel, The Mediterranean Caper, was written on a card table in the back of a skin-diving equipment shop where Cussler had taken a job to "absorb the right atmosphere." Caper was a modest success, but Cussler didn't become famous until 1976 and the publication of Raise the Titanic!, which got mixed reviews but sold more than three million copies. "I'm not a great writer of literature," concedes Cussler. "I'm an entertainer."

The profits of entertainment have brought Cussler a four-bedroom house in Denver, which he shares with Barbara, 51, his wife of 28 years. (They have two daughters, ages 20 and 26, and a son, Dirk, 23, after whom Pitt is named.) Apart from writing or looking for lost ships, Cussler coddles his collection of 28 antique and classic cars, including a 1918 Cadillac once owned by Gloria Swanson and F. Scott Fitzgerald's 1923 Renault. (Dirk Pitt also collects vintage autos.) Although most of his readers can't afford such toys, Cussler believes they identify with his intrepid hero. "There's a little bit of Pitt," he adds with a wry smile, "in everybody."