An ironclad battleship, lost since the Civil War, is found in the Sahara desert by explorer Dirk Pitt (Matthew McConaughey), who uses the ship's ancient cannons to defend himself, his Italian buddy Al Giordino (Steve Zahn) and Dr. Eva Rojas (Penelope Cruz), the babe scientist they just happen to have on board. The enemy is the African dictator (Lennie James) who is now strafing them from his chopper.

That cool scene and others like it — a nifty chase in a high-tech speedboat that Pitt borrows from an admiral (William H. Macy) — persuades you to cut Sahara some slack. First-time director Breck Eisner — yes, he is the son of Disney chairman Michael Eisner — keeps the pace zippy, the lulls short and the actors from bumping into each other. OK, you could wish for the sly wit of Raiders of the Lost Ark and dialogue that doesn't give you Indy-gestion. Fans of novelist Clive Cussler — Sahara is the eleventh of his eighteen Pitt best sellers — are bound to be wary. Cussler, 73, is still miffed that Hollywood botched Raise the Titanic, the 1980 film flop with Richard Jordan as Pitt.

McConaughey, despite alarmingly orange makeup, does justice to the role, a hard-drinking, shipwreck- hunting senator's son with a 007 way with the ladies. There's a lot of Pitt in Cussler, who has discovered more than sixty shipwrecks and ted the National Underwater and Marine Agency, the nonprofit group that Pitt works with in the movie. Zahn, despite looking and sounding more like a surfer dude than the book's brawny Italian stallion, pushes for laughs and gets them. And Cruz, despite her still-indecipherable English, gets in more fem-warrior licks than Cussler ever wrote for the doc. Subplots abound involving slavery, gold and nuclear-waste pollution on its way to the U.S. But there's no disguising the fact that Sahara has all the heft of marshmallow.