Clive Cussler, the prolific author whose adventure novels like Raise the Titanic! and Sahara have become classics of the genre, has died at 88, the New York Times reports.

Cussler’s death was confirmed on his official Twitter account by his widow, who wrote, “It is with a heavy heart that I share the sad news that my husband Clive passed away Mon. It has been a privilege to share in his life. I want to thank you his fans friends for all the support. He was the kindest most gentle man I ever met. I know, his adventures will continue.”

Cussler, an Air Force veteran, got his start in the advertising industry. In 1973, he published The Mediterranean Caper, the first novel to feature his now iconic hero Dirk Pitt, a Vietnam War veteran and marine engineer with a knack for getting embroiled in oceanic adventures.

He would go on to write 24 more novels featuring Pitt, including Iceberg, Treasure, and Dragon. The final Pitt novel to be published in his lifetime, Celtic Empire, was released last March.

Cussler was himself an adventurer with a taste for underwater exploration. He founded the nonprofit National Underwater and Marine Agency, a group that discovered several shipwreck sites, including those of the RMS Carpathia and the CSS Manassas.

On Twitter, his admirers mourned his death. “RIP Clive Cussler,” wrote author Roxane Gay. “I love love love his books.”

And writer James Rollins tweeted, “We lost a literary icon, a true lion of adventure fiction—and a personal inspiration of mine. I’ve mentioned Clive Cussler at every signing as one of the reasons I write today.”

Michael Schaub is an Austin, Texas–based journalist and regular contributor to NPR.