Nessie lays an egg both literally and figuratively in this inoffensive, visually attractive but highly derivative family movie about a boy and his beastie. “The Water Horse: Legend of the Deep” is set in World War II Scotland, specifically the coastal areas adjacent to Loch Ness, and its young hero is Angus (Alex Etel), the young son of Anne MacMorrow (Emily Watson), the housekeeper at a large estate whose noble master has gone off to fight. Angus is a morose, lonely lad, in denial over the fact that his dad (Craig Hall) has been lost in the sinking of a ship ferrying troops to the continent and will probably not return. He finds what he originally thinks is a curious rock along the shore of the loch and brings it home, only to find that it’s an egg that hatches to produce a lizard-like, water-loving thingy that he quickly adopts and conceals from his mum. Eventually he’s forced to share his secret with his older sister Kirstie (Priyanka Xi) and Mowbray (Ben Chaplin), the moody handyman hired by Anne, who has a secret in his past (of course) and suggests that the beast might be the legendary water horse—a creature of which only one exists each generation, supposedly spawned from an egg laid by its predecessor immediately before its death.

Naturally the story needs some conflict, so that’s supplied by Captain Hamilton (David Morrissey), the head of a contingent of troops billeted at the estate to set up guns and nets designed to trap and destroy any German subs that might find their way into the loch. He grows interested in Anne and suspicious of Mowbray, and takes it upon himself to “make a man” of Angus. He also brings with him a few men (Marshall Napier, Joel Tobeck and Erroll Shand) who grow increasingly curious about what the boy might be hiding, especially after the company dog sniffs the fast-growing, rambunctious beast out. And there’s one more major character: a modern-day old duffer in the local bar, who tells the entire tale to a couple of young tourists in what are essentially extended flashbacks. He’s played with canny gruffness by Brian Cox, whose periodic intrusions to respond to his listeners’ prodding and protestations recall Peter Falk’s similar interruptions in “The Princess Bride.”

But it’s not that Rob Reiner picture that “The Water Horse” seems to copy. It will be widely compared to “E.T.,” and with considerable justification, but what Robert Nelson Jacobs’ script (based on a novel by Dick King-Smith) actually resembles is a blending of that Steven Spielberg classic with the recent (already cancelled) NBC teleseries “Surface,” minus that show’s conspiratorial elements. But that’s not all: by the end, when little Angus is actually being carried about by his pet, which he names Crusoe, the picture veers into “Whale Rider” territory, before recycling “Free Willy” at the close. And to add to that, the CGI-fashioned face of Crusoe seems to have stepped out of a Dr. Seuss book—the look and expressions are those of the Grinch, after his conversion to the light side, of course. (But perhaps I’m being unfair: there’s a good bit of Bob Clampett’s Cecil the Sea-Serpent in Crusoe, too.)

Of course, all the familiarity might not bother either the kids at whom “The Water Horse” is aimed or the parents looking for some child-friendly holiday entertainment. In fact they might find it a virtue, even when it comes to so cliched a sequence as the one where Crusoe is chased around the mansion by the soldiers’ dog, with resultant slapstick destruction of course. (And it’s a scene repeated a second time, just in case you didn’t get enough of it.)

On the positive side, the scenery (much of it in New Zealand, subbing for Scotland) is lovely, and is nicely caught by Oliver Stapleton’s sumptuous cinematography. The cast is likable, with Etel in particular charmingly poker-faced as young Angus and Chaplin nimbly juxtaposing Mowbray’s light and dark sides. (Watson and Morrissey, by comparison, come across as rather stranded in their more serious roles,) The computer animation is adequate though hardly outstanding by contemporary standards, and Tony Burrough’s production design, along with Dan Hennah’s art direction and John Bloomfield’s costumes, captures the period well. The prolific James Newton Howard’s score does what’s expected of it—perhaps too well. And director Jay Russell knows his way around this kind of material, although it must be said that he doesn’t seem to have quite the rapport with a computer-generated critter as he did with the authentic pooch of “My Dog Skip”—a distinctly better film.

But though “The Water Horse” is pleasant to look at and certainly good-natured, a really good picture about the Loch Ness monster has proven as elusive as the beast itself. And this one is no exception.