(CNN) There's a great special to be made about "Titanic," the movie; and Titanic, the giant ocean liner that sunk 105 years ago. "Titanic :20 Years Later With James Cameron" splashes down somewhere between the two, and in the process almost completely misses the boat.

Produced by Cameron, and coinciding with an anniversary re-release of the film and a related book, the special focuses on the veracity of the movie, and how well its conclusions have held up as new revelations about the ship and its sinking have arisen in the years since the film.

The result, though, is a pretty wonky look at the science of all that, including experiments and reenactments designed to illustrate precisely how the ship went down, or how long it would have taken for a man with a knife to cut lifeboats loose.

It's moderately interesting, in the way almost everything about the Titanic is, beginning with oceanographer Bob Ballard, who discovered the wreck more than 30 years ago while on a secret mission for the U.S. Navy. And Cameron's passion for and knowledge of the subject obviously shines through.

The special also seeks to incorporate a more human element, with Cameron interviewing descendants of passengers who either survived or perished aboard the ship, including relatives of John Jacob Astor, Molly Brown, and Isidor and Ida Straus. It's a promising idea, but mostly plays like an excuse to have these family members pat the director on the back for how moving they found the film to be.

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