SHARKS 3D — ** 1/2 — Large-screen documentary about sharks; rated G (animal violence).

The latest IMAX film — "Sharks 3D" — is such a beautifully shot and well-intentioned film that you feel bad saying anything bad about it. But the truth is, there's not much to this lovely "immersive experience" except the opportunity to gape up-close at a bunch of endangered species in their underwater home.

The film is an apparent public relations effort to improve the image of the shark from man-eater to noble, threatened creature. A friendly turtle (voiced by Geoffrey Bateman) plays tour guide for a quick (42 minutes) visit with "the lions and tigers of the ocean." They are, he tells us, "picky eaters" that don't eat what doesn't taste good to them — "people, for example."

According to the voice of the turtle, sharks have been in existence for millions of years — before the dinosaurs, even — yet industrialized civilization has managed to deplete some species' numbers by perhaps 80 percent in the past 10 years alone. How? Well, guess. Pollution, fishing, torment by tour boat? Turtle doesn't tell us.

Filmed during 500 hours of diving from October 2003 to June 2004, "Sharks 3D" does present some magnificent images of undersea life. The fish appear to surround the viewer, giving the sensation of diving with them. It is a very close encounter with sand tiger sharks (endangered), silver-tip sharks (endangered), great Pacific manta rays (endangered), sawfish (critically endangered), great white, great hammerhead, silky and reef sharks (all endangered) and scalloped hammerheads and whale sharks (both critically endangered).

With the best of intentions — to end the sharp decline in the shark population and raise general awareness of the need to preserve the ocean and its denizens — "Sharks 3D" skims the surface and doesn't offer much depth. It manages to convey little real information or inspire action.

But it's fun to watch and it won't scare kids. Perhaps teachers can use the educator's guide that's available with the film to make it a learning experience.

"Sharks 3D" is rated G. Running time: 42 minutes.