It’s all about everything

Scenarist Robert Nelson Jacobs (”The Shipping News,” “Chocolat”) has brought some conventional dramatic hooks to bear on Dick King-Smith’s slim tale about a 1930s family adopting an increasingly hard-to-manage sea monster — namely, making the story’s protagonist a lonely, emotionally troubled young tyke and recasting the events against the war-torn ’40s.

Set in the Scottish region bordering the giant lake known as Loch Ness, the boy-meets-egg saga kicks off with Angus MacMorrow (Alex Etel, “Millions”) discovering a rock-encrusted object washed ashore one morning, which he takes back to the sprawling estate where he lives with his housekeeper mom Anne (an excellent Emily Watson) and older sister Kirstie (Priyanka Xi). When a purplish creature resembling a baby dinosaur hatches from the egg, Angus immediately decides to secretly adopt the raucous little beastie.

Crusoe, as Angus names the slimy castaway, has a horselike snout, webbed feet, Shrek-like ears and a marked affinity for water. (There are also traces of dog, eagle and giraffe present, at least according to the press notes.) Eating and growing at a persuasively alarming rate, the creature soon gets too big for the bathtub, threatening discovery by Angus’ stern mother.

Complicating matters are the British soldiers stationed at the house, under the rather bogus pretext that German subs are expected to pass through the loch. While Anne flirts with the dashing but smug Capt. Hamilton (David Morrissey), the script duly trots out handsome, hard-drinking handyman Lewis Mowbry (Ben Chaplin), who bonds with Angus and Kirstie, helps them keep Crusoe a secret, turns out to have a military record even more distinguished than the captain’s, and in general couldn’t be more likable to auds if he defeated Hitler singlehandedly.

Yet despite the obvious setups — and the potential mawkishness of Angus’ memories of his dad (played by Craig Hall in flashback) before the latter left for the frontlines, never to return — “The Water Horse” never drowns in bathos. Director Jay Russell (who also helmed such family fare as “Tuck Everlasting” and “My Dog Skip”) displays a sensitive touch with conventional material, nurturing the story’s slapstick potential (i.e., when a soldier’s dog realizes there’s another animal on the premises) without going overboard.

Just as the creature quickly swells from pint-size pet to gargantuan behemoth, necessitating its relocation to the Loch Ness, so the film transitions seamlessly from a gently spirited comedy to a harrowing drama that might prove frightening to especially wee tots. As Angus fights to protect Crusoe from the eyes and cannons of the British militia, the pic quietly captures the frustration and dangers that plagued even those on the sidelines of the Good War, most notably in Watson’s deeply felt performance as a single mother struggling to hold on to her sanity.

Vividly rendered by the visual-effects artists of Weta Digital (also behind “The Lord of the Rings” trilogy and “The Chronicles of Narnia” franchise which, like this film, was produced by Walden Media), with especially close attention paid to the creature’s gradual metamorphosis, Crusoe never quite makes viewers forget they’re watching a ginormous special effect, but comes close enough to establish the poignant, all-important bond between boy and beast. Supporting thesps are uniformly strong, including Brian Cox in an affectionate turn as the story’s present-day narrator.

Oliver Stapleton’s sweeping widescreen compositions are gorgeous enough to jumpstart Scottish tourism (though New Zealand locations subbed extensively), while the surging score by James Newton Howard (who turned in subtler work on this year’s “Michael Clayton”) overdoses a bit on the bagpipes and Celtic overtones.

Though the pic is being marketed as “The Water Horse: Legend of the Deep,” the title on the print screened read simply “The Water Horse.”