Grade: B+

After a long absence from the big screen (he spent a good deal of time on his since-canceled Fox series “Dark Angel”), James Cameron returns to what’s surely his signature subject–the Titanic–in “Ghosts of the Abyss.” He does so on an even larger canvas than before–spatially, not temporally–with an hour-long IMAX documentary recounting an expedition to descend in miniature submarines to the actual wreckage of the doomed liner on the bottom of the Atlantic and explore the remnants with specially-designed robotic cameras. Sumptuously produced in IMAX 3-D and cannily designed to generate suspense along the way, the film is a voyage of discovery that’s generally absorbing and sometimes breathtaking, though some of the directorial choices are unnecessarily glitzy.

The expedition, undertaken in the fall of 2001, made use of the specially-designed Reality Camera System, which incorporated digital technology to create instruments that could shoot hours of 3-D footage underwater in the wide image format, and entirely new camera housing capable of withstanding 6,000 pounds of pressure per square inch. It also employed two Remotely Operated Vehicles, originated named BOT 1 and BOT 2 but later called Jake and Elwood, that could be maneuvered to prowl inside the debris from the Russian submersibles that carried Cameron and the crew down to the ocean floor. What results are haunting images which the director complements with elaborate CGI reconstructions to show what the areas originally looked like. Old footage and stills are used to provide further context, and bits of Cameron’s 1997 Oscar-winning epic offer occasional bursts of epic sweep. The picture is personalized by focusing on actor Bill Paxton, who accompanied Cameron and narrates the piece as a suitably nervous and awestruck participant.

Most of Cameron’s choices here are very effective. Visually the film is impressive indeed, especially in the underwater sequences, and the maps and digital recreations he uses to clarify the topography of the wreckage are excellent. He also makes Jake and Elwood such likable contraptions that one actually feels concern when one of them might be lost; the duo is almost like a lesser version of R2D2 and C3PO. Where he goes astray is in staging scenes from the last hours of life aboard the Titanic, done in elaborate but stilted fashion, and then inserting them like ghostly recollections into the narrative. The idea might be sound and the execution slick, but the people seem almost like waxworks figures (a fate that also befell some of the characters in Cameron’s “Titanic”).

As a whole, however, “Ghosts of the Abyss” is an impressive achievement, especially from the technical perspective, and a fascinating tour of a legendary site. The picture is dedicated to the late Walter Lord, whose book “A Night to Remember” was the basis for the splendid, documentary-style British film of 1958 on the maritime disaster.