There’s a lot to be said for movies that use the ever-improving state of the digital art to recreate historical events too expensive to film in the old fashioned way.

And the digital Japanese kamikaze planes, submarine and the recreated heavy cruiser U.S.S. Indianapolis are convincing enough in “U.S.S. Indianapolis: Men of Courage.” So are the shark attacks that animate this awful “true story” of the sea.

But a melodramatic, overreaching and sometimes just inaccurate script by Nic Cage’s go-to screenwriters undermines director Mario Van Peebles’ World War II epic.

Cage stars as Captain Charles B. McVay, skipper of the battle-scarred warship selected to deliver the atom bomb to the island airbase where it will be flown to Hiroshima, a mission that will “shorten the war” and save “millions of lives,” his commanding officer (James Remar) tells him.

It’s the sort of role that Cage sees too seldom here in the C-movie stage of his Oscar-winning career. It’s a pity the part is wasted in a film that fails to measure up to its subject.

The Indy, if you remember your history or your “Jaws” speeches, delivered that A-bomb in pieces to be assembled on Tinian, where the B-29 Enola Gay would take it into history. The cruiser’s mission was top secret, and in an effort to keep the number of people who knew about it small and the chances the enemy would know something was up, she was sent alone, without destroyer escort, to make that delivery.

Afterwards, on the way back east, she was sunk by a Japanese submarine. The Navy, having hidden her trip from one and all, didn’t realize she’d been sunk. Rescue for the survivors was slow in coming. But not the sharks.

Writers Cam Cannon and Richard Rionda Del Castro (“Rage”) pepper the tale with anecdotal scenes, giving us a story that cuts far wider than it needs to and reaches for metaphors it never grasps.

Sailors on leave, drinking and brawling, the guy with the lost engagement ring to a girl whose daddy doesn’t approve of him, the racial tensions on board, the aspiring African American writer (Craig Tate) stuck in the galley (kitchen), the spoiled Admiral’s son (Callard Harris) whom every member of the crew hates — a lot of this background material isn’t necessary, and just as much of it isn’t true.

A quick online perusal of the list of survivors points out more than one bit of invention in the cause of “dramatic license.” If these were real people and not “characters,” why change their names at this late date?

Some of the “types” make an impact, on screen. Tom Sizemore is well-cast as the Chief Petty Officer whose job it is to point out that the ship is an unlucky 13 years old, and that sharks are the “top of the food chain” in the world where they’re operating. His speeches may be peppered with anachronisms, but he makes them work.

The screenplay finds villains, and makes some more up. Any film on this story is going to second-guess the Navy, the captain (who was court-martialed and posthumously  exonerated).  But if real people committed the various acts of cowardice, classism and racism depicted here, why not name them instead of inventing a Lt. Standish?

The shark attacks are jarring, the recreation of the moment of torpedo impact well-handled and vividly recreated. But the whole affair lacks a coherent point of view. When you start with backroom politics about the decision to drop the bomb, when you take the time to ennoble the Japanese foe, when you suggest dog eat dog survival situations and you jab officious mid-level shore officers for ignoring the SOS, and then devote the third act to the court case, you’re biting off more story than you can do justice to.

The 1991 Stacy Keach TV movie “Mission of the Shark” wasn’t as ambitious, but the focus was sharper and it held together better. With genuine heroes on board who survived the tragedy, why invent sailors and back-stories and melodramatic cliches that play as “Hollywood” corn?

As “The Greatest Generation” dies off and the number of films that tell their stories dwindles, it’s important for every outing to be as accurate as you can make it within the limitations of the form. “Men of Courage” doesn’t do justice to those men by being as half-hearted and clumsily-scripted as this film is.

MPAA Rating:R for war-related images and brief language

Cast: Nicolas Cage, Tom Sizemore, Craig Tate, Adam Scott Miller, Callard Harris, James Remar, Yutaka Takeuchi, Thomas Jane

Credits: Directed by Mario Van Peebles, script by Cam Cannon, Richard Rionda Del Castro. A Saban Films release.

Running time: 2:10