Although Pacific Vortex is considered the first of the Dirk Pitt novels, it was not the first to be published. In the Forward, Cussler explains (Sphere Book edition 1983):
Not that it really matters, but this is the first Dirk Pitt story.
When I mustered up the discipline to write a suspense / adventure series, I cast around for a hero who cut a different mould. One who wasn’t a secret agent, police detective, or a private investigator. Someone with rough edges, yet a degree of style, who felt equally at ease entertaining a gorgeous woman in a gourmet restaurant or downing a beer with the boys at the local saloon. A congenial kind of guy with a tinge of mystery about him. Instead of a gambling casino or the streets of New York, his territory became the sea, his challenge, the unknown. Out of this fantasy, Dirk Pitt materialised.
Because this was his first adventure and because it does not weave the intricate plots of later exploits, I was reluctant to submit it for publishing. But at the urging of friends and family, fans and readers, Pitt’s introduction is now in your hands. May it be looked upon as a few hours of entertainment and, perhaps, even a historical artifact of sorts.
More information is available in the book Clive Cussler and Dirk Pitt Revealed – by Clive Cussler and Craig Dirgo (Pocket Books 1998):
As one of the two manuscripts originally sent to Peter Lampack when Clive was seeking an agent, it languished on a shelf in Clive’s closet until he casually mentioned it to his publisher, which at that time was Bantam Books. Upon learning that there was an unpublished Pitt novel, it was decided to introduce the book in a paperback-only edition. Clive dusted off the manuscript and did a quick rewrite. The name of the villain Delphi Ea was changed somewhere along the line to Delphi Moran, something that Clive was still unaware of when it was mentioned to him last year.
One interesting fact, and I am only going by memory here (as such I may have my facts wrong), is that Dirk Pitt was not originally intended to be the continuing hero of Cussler’s books. Many years ago, I borrowed from my local library a Hardcover edition of The Mediterranean Caper. In the introduction to that book, Cussler explains that he originally intended for the villain, Delphi Ea, to be the continuing character – popping up all around the world – causing all sorts of mischief. But later Cussler changed his mind and went with Pitt. I wish I could get hold off that particular Hardback again (the paperback edition, which is quite easy to find, doesn’t have the introduction by Cussler).
From the back:
SEA TERROR! Fully armed and with all hands on board the nuclear submarine Starbuck sailed into the calm Pacific Ocean for sea trials – and vanished. No wreckage, no signals, no survivors: nothing… until ace maritime troubleshooter Dirk Pitt finds a single, chilling clue in the shark-torn surf off Hawaii – the log of the Starbuck. ‘Do not search for us, it can only end in vain…’ A crazed journal of madness and death is all that remains. And the Captain’s final, scrawled, fear crazed note locates the Starbuck’s grave hundreds of miles from her last known position! The search for the Starbuck plunges Dirk Pitt into his most shattering assignment to date – a whirlpool of deep-sea mystery and terror – the PACIFIC VORTEX!