It's a wonder Clive Cussler's fictional character Dirk Pitt hasn't made it onto the big screen already: scuba diver, treasure hunter and adventurer, he's a man's man who's got a way with the ladies, an all-around action hero with an appreciation for classic cars. He's been the star of best-selling books for more than 30 years and seems custom made for large-scale luminous projection.

Clouding reality is the fact that NUMA, the National Underwater and Marine Agency, for whom the fictional Dirk Pitt works, was actually founded by author Clive Cussler and is a real nonprofit exploration organization that's discovered more than 60 shipwrecks. Cussler is, of course, a scuba diver and treasure hunter with an extensive collection of exotic classic cars. I have no personal knowledge of his luck with women, but a certain physical likeness between Matthew McConaughey and Cussler is hard to deny, so you can draw your own conclusions there.

McConaughey and sidekick Steve Zahn do a great job in Sahara, effortlessly inhabiting their action-hero skins as if they were born to them, and their comfort puts the audience at ease and makes Sahara a lot more fun than it might otherwise be. They laugh when they blow stuff up. They're like a couple of college kids on spring break, tearing through Africa on a grand adventure, getting sidetracked to help that hot girl they met from the World Health Organization (Penelope Cruz). Sure, they're kind of obnoxious, but they've got a speedboat and you, my friend, do not.

The movie is marked by sure-footed charisma throughout, from the natural banter between Cussler-I mean Pitt-I mean McConaughey-and Zahn, to the smooth performance of Lennie James as bad General Zateb Kazim. When James surveys a demolished town and says, "...And find the girl. She's here... somewhere," just before adjusting his sunglasses and stepping back onto his war-helicopter, it actually doesn't suck. The line, like so many others in Sahara, is delivered with such aplomb that it just works.

Sahara is not without flaws. It drags in the final third, the story has some holes, and the plot's centerpiece peril ends up having something to do with pollution that seems to have been accidental, so that's a little anticlimactic. There's also a plague that seems really important at the beginning of the movie, but disappears at the end.

But the strength of the characters carries us through and leaves us wanting to go along on more of their adventures.

Did I mention that Cussler uses the royalties from his Dirk Pitt books-and presumably from this movie-to fund NUMA's real-life underwater expeditions? It's hard to decide which character, Pitt or Cussler, is more appealing, but the qualities of both help shape Sahara.