When the tsunami slammed into Phuket, it did more than kill tens of thousands of people. Creatures from miles beneath the sea were washed ashore, many of them like something out of an extraterrestrial zoo. The premise of director James Cameron’s new Imax documentary, Aliens of the Deep 3D, is that learning about these strange beings, which thrive in a place once thought incapable of supporting life, gives us the next best thing to an encounter with life-forms from another planet.

Fans of Cameron’s sci-fi action movies may be disappointed to learn that this is not a cross between Aliens and The Abyss—though Disney’s ad people have been happy to suggest that it is. It was The Abyss that sparked Cameron’s fascination with the ocean depths, leading to Titanic and then to Ghosts of the Abyss (2003), his Imax documentary about his real-life expedition through the ship’s wreckage. But there’s plenty of evidence here that he’s still a director first and an explorer second.

When Imax 3-D theaters first opened 15 years or so ago, filmmakers seemed to grasp the potential posed by the format’s huge frame and startling illusion of depth. With the audience virtually inhabiting the film’s space, standard techniques like quick cutting produce entirely different effects, while even a locked-down camera can pull an audience into a scene as never before. But when films like Jean-Jacques Annaud’s Wings of Courage (1995) failed to bring in the huge audiences necessary to support the expensive technology, offerings began descending to the level of theme-park attractions, reaching a nadir with the stomach-churning roller-coaster sequence that had people bolting out of Encounter in the Third Dimension (1999).

As the bulky helmetlike viewers of the 90s have given way to thin plastic glasses, productions have gone more in the direction of the Bell Science Specials of the 50s, setting up rough story structures to teach scientific subjects to children. Aliens of the Deep 3D belongs in this category to a certain extent, though it also makes an effort to engage adult viewers. Cameron, who got his first taste of 3-D with T2: Battle Across Time (1996), clearly understands that, for young or old, simple devices work best in the format. He starts with some dazzling time-lapse shots and continues with an elephant that puts its trunk right in your lap.

But the best parts of the film come when the underwater cameras simply record the wonders on hand around volcanoes three kilometers below sea level. Expanding on some of the sights captured for the Imax film Volcanoes of the Deep Sea (2003), which Cameron produced, the 3-D photography takes us to a corner of the world where heat vents spew gases into the water under intense pressure and the sun never shines. It would seem nothing could possibly live here, yet we’re shown creatures in abundance: ethereal rings of tissue swim about like ghosts, huge worms consume nutrients despite lacking stomachs, millions of shrimplike animals swarm over beds of wispy bacteria. Framing a shot of a squid with gently flapping flippers on its head and white, downy-looking skin, Cameron remarks that he “could watch this guy all day.”

Other facets of the production suffer by comparison. While in Ghosts of the Abyss Cameron gave us a sense of what the team’s mission was, here we know only that Cameron and his bright-eyed young scientists (who take turns narrating) are heading to the deeper parts of the Atlantic and Pacific to observe the environment and life-forms down there. And most of the intended humor falls flat. Seismologist Maya Tolstoy is introduced as a teacher who can “make science fun,” which she demonstrates by making a funny face at the camera—yep, she’s the Patch Adams of marine geology.

The film’s true worth is in revealing the life at the bottom of the sea, and after this the intended climax of the show comes as a bit of a letdown. Visual effects supervisor Chuck Comisky gets in on the action by digitally imagineering a space mission to the moons of Jupiter that’s in the planning stages at NASA, beautifully rendering a voyage beneath the ice of Europa, where the young scientists encounter an alien civilization much like that in The Abyss. It’s a nifty sequence reminiscent of Disney’s old Man in Space programs, but it can’t measure up to the true-life wonders we’ve just witnessed. Even with all these gigabytes at his disposal, Cameron gets more of a reaction with the old trick of having something jump in front of the camera.