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The IMAX theatres have offered a host of deep-sea documentaries over the years, and by comparison the conventionally-shot “Deep Blue” seems a trifle small-scaled, at least in terms of screen size. It tries to make up for that, however, by running for a full hour and a half–which, unfortunately, may be a bit too much of a reasonably good, but not outstanding thing.

The picture, laboriously assembled over three years’ filming in a wide variety of locales, has been likened to “Microcosmos,” the 1996 feature that focused its special cameras on the insect life of a field over the course of a single day. But the comparison isn’t terribly apt, because while the earlier picture was a concentrated study of the confined area–which gave a sense of structure to the whole–this one roams without much apparent organization over the widest possible regions. The result is that while individual sequences are impressive, they don’t make up as cohesive an experience. On the other hand, the makers aren’t reluctant to include material showing that in the oceanic environment the struggle for survival is certainly paramount. Some viewers may find a prolonged sequence involving a young whale being fatally attacked by a group of predators while its mother struggles to fend them off hard to watch, and the same is true of an episode in which seals are the quarry. Though “Deep Blue” is clearly intended for family viewing, such scenes may prove too strong for younger children.

One might also note that some of the content is reminiscent of earlier documentaries. The portion dealing with penguins engaged in their mating rituals, for instance, doesn’t do the same justice to that fascinating phenomenon that “March of the Penguins” does. And when the cameras venture deep underwater to capture mini-volcanos at the bottom pumping out black smoke and creatures huddling upon the rocks, as well as luminous, almost otherworldly species that live at the furthest depths, the images are impressive, but similar visuals have already been shown to greater effect in James Cameron’s “Aliens of the Deep.”

Perhaps the package would be more compelling if it weren’t burdened with a narration that’s not only less informative than it might be but is delivered by Pierce Brosnan in drowsy tones that seem designed to lull us rather than pique our interest. George Fenton’s score isn’t as imaginative as one might wish, either.

Of course, it’s the footage that matters here, and much of it is very impressive. It’s just a pity that it hasn’t been laced together to create a real arc rather than a series of isolated episodes, or joined to words and music that would enhance the images rather than simply accompany them. “Deep Blue” is interesting without being fascinating in the way that “Microcosmos” certainly was. You can safely await its appearance on the small screen in your own home.