“The Finest Hours” is a rescue-adventure film set in 1952 that wishes it were set during World War II. It tells the real-life story of an improbable Coast Guard mission to save a distressed oil tanker during a massive storm. The film’s nostalgic glow and mawkish sentiment, however, wind up diminishing a heroic feat by blowing it out of proportion.

The story’s hero is Bernie Webber, an unassuming Coast Guard captain in Chatham, Massachusetts, played by a very good Chris Pine (marking a departure from his cocky Captain Kirk in “Star Trek”). In the film’s long preamble, Webber and his pal Gus (Beau Knapp) go on a double date in a soda shop. Webber’s girl, Miriam (Holliday Grainger), will soon become his fiancee. The old cars, quaint atmosphere and New England accents tell us we’re in a better, nobler time and place.

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When a nor’easter hits, the SS Pendleton literally cracks in two, leaving more than 30 men stranded on a sinking hulk. Casey Affleck plays first assistant engineer Ray Sybert, a loner who reluctantly finds himself in charge. Back on shore, Warrant Officer Daniel Cluff (Eric Bana) orders Webber and a small crew to take a tiny rescue boat into the raging waters.

This should be a riveting story, but “The Finest Hours” fails to make it so. Director Craig Gillespie (“Lars and the Real Girl”) has an eye for big-scale spectacles — the giant waves and sheared tanker are impressive — but the details escape his grasp. It’s hard to understand, visually, what Sybert is doing to save his ship, or what underwater dangers threaten Webber’s boat. The characters try to explain it, but the script (based on the 2009 book) is a confusing deluge of maritime terminology. The result is discombobulation rather than white-knuckle tension.

If “The Finest Hours” had presented us with a group of men simply doing their duty, it might have been more effective. Instead, it tries to conjure up Normandy and Iwo Jima with images of glowing young faces in uniform and Carter Burwell’s swelling score (not to mention the film’s Greatest Generation title). In this movie, a little less would have gone a long way.