Grade: C+

Since becoming the self-proclaimed king of the world with “Titanic,” James Cameron has shied away from fiction filmmaking almost as assiduously as George Lucas did in the wake of the original “Star Wars.” But instead of concentrating on writing scripts to be put on screen by other directors and pushing forward the science of special effects as Lucas chose to do, Cameron has continued to feed his fascination with the ocean floor, now from a documentary perspective (although, by embracing the IMAX format, first in “Ghosts of the Abyss,” which investigated the interior of the actual Titanic wreckage, and now in this picture, he certainly shows a similar penchant for cutting-edge cinematic technology). “Aliens of the Deep” uses the same revolutionary deep-water submersibles and robotic cameras that he employed with stunning results in “Ghosts” to photograph the unusual life forms and curious geological phenomena of the deepest ocean bottoms. He takes along scientists researching the possibility of extraterrestrial life because the search techniques developed for his expedition are the closest that can be attempted on earth to those that might be required, for example, to penetrate the secrets of the waters lying beneath the ice on the moons of Jupiter; and at the end of the picture we get an imaginative–indeed, over-imaginative–picture of what an initial encounter with creatures living in such an outer-space environment might look like. (Just think of an underwater version of “Close Encounters of the Third Kind.” And despite the Jupiter locale, happily no black monolith is involved.)

It’s impossible not to be impressed by Cameron’s dedication to this sort of exploration, and some of the images are remarkable–a shimmering creature that looks like a gossamer cloth floating through the waters, a rare giant squid grabbing onto the submersible, tiny volcano-like protrusions pouring out hyper-heated black steam on the ocean floor–but there’s too much repetitive footage of shrimp clustering around food sources (and clinging onto the robot camera) and of the awestruck faces of the team as they repeat banal exclamations like “It’s incredible!” or “How beautiful!” (It’s as though the filmmakers felt it necessary to prompt the viewer’s reactions.) The result is that though “Aliens of the Deep” is only 48 minutes long and the 3-D effects are sometimes stunning, it has substantial passages that are curiously dull. And the concluding CGI episode, featuring extraterrestrial beings that look like big, luminous snails minus the shell, wouldn’t pass muster in a feature film.

If the fictional portion of the movie is any indication, it’s probably all for the best that Cameron has elected to hold off on his writing for awhile. (After all, that’s always been his weakest suit–witness the fact that the script for “Titanic” was about the only thing in that movie, apart from the acting, not nominated for an Oscar, and Cameron co-wrote the awful “Strange Days.” In this Cameron is clearly distinct from Lucas, who’s written some solid material but has been a bust as a director–witness his unhappy return in that capacity in the last two “Star Wars” episodes–while Cameron’s direction has always been superb in the popcorn movie sense, even if his writing is usually pretty pallid.) This underwater “Aliens” isn’t terrible–it has its moments, even though as a whole it’s just mediocre–but it can’t hold a candle to Cameron’s other “Aliens”–the one from 1986. Would that he’d rediscover the wonderfully pulpy attitude that animated that movie (and the first “Terminator”) and give us more of the same instead of acting like a tour guide from the Natural History Museum.