Well, were you expecting “Citizen Kane?”

If you got the impression from the previews for “Into the Blue” that this movie is a bunch of nubile, tan young actors doing a lot of diving, fighting, kissing, more diving, arguing and still more diving, you’d be right. So it’s not going to win any Oscars – but a couple of good performances and some striking cinematography save this movie from drowning in shallow cheesiness like most of its ilk.

Anchoring the cast are Paul Walker (“The Fast and the Furious”) and Jessica Alba (“Fantastic Four”) as a happy-go-lucky couple living in the Bahamas, eking out a living from the tourist industry and dreaming of the day they can afford to become full-time treasure hunters. This is flawless casting. I can’t imagine any other two actors playing these parts so effortlessly. And the scruffy look suits them both – especially Alba, who benefits from losing the Invisible Woman coif.

Once audiences get the very clear message that the pair would rather be happy than rich, Walker and Alba join up with visiting friend Scott Caan and his very new girlfriend, leggy fashionista Ashley Scott. Caan’s a frat boy-turned-attorney, and he manages to score the quartet the use of a beachfront mansion and yacht courtesy of a former client. Off they go to dive and snorkel their hearts out … oh, and maybe look for treasure while they’re down there.

Hints of which, of course, they find, teasing them onward into waters infested with sharks, competing treasure hunters, corrupt cops and a plane wreck hiding millions of dollars worth of cocaine.

Moral dilemma! They don’t have enough money to rent the equipment to properly salvage the treasure, which turns out to be a legendary French ship loaded with gold. The characters’ true characters come to light over the debate: Should they sell enough of the drugs to finance their quest before turning the plane over to the authorities?

It wouldn’t be a very exciting movie if they all agreed to leave it alone, would it? (Fending off sharks with a mop is a nice bit, but you can’t stretch it out for an hour.) Enter the villains, some really scary baddies with all sorts of henchmen and weaponry. Rival salvager Josh Brolin (of “The Goonies” fame) adds a threat as well.

Director John Stockwell (“Blue Crush”) claims 70 percent of “Into the Blue” was shot at or below the waterline, making the most extensive use of underwater moviemaking since “Thunderball.” I tend to believe him. Alba and Walker are completely at ease in the depths, whether in full scuba gear or free diving. (Costars Caan and Scott trained to become certified divers for the film.) And all those sharks? Real, not digital. Viewers share in the actors’ excitement over the unpredictable shooting conditions and untrained wildlife that naturally dresses every undersea set.

Once in a great while, Hollywood turns out a piece of fluff that’s not a complete waste of the studio’s money and audiences’ time. “Into the Blue” may indeed be fluff in the grand scheme of filmdom, but don’t be surprised if you find yourself trying to hold your breath along with Paul Walker as he combs the ocean floor for glimpses of gold.