IF you've ever sat and watched a movie and thought to yourself, 'Wow, a seven-year-old could have come up with this', you're going to have something to say about The Adventures Of Sharkboy And Lavagirl In 3-D.

Because a seven-year-old really did spark the idea for this gaudy family film. No, seriously.

Director Robert Rodriguez's son Racer conjured the characters and landscapes of the movie while chatting to his father about superheroes.

Unfortunately, Rodriguez (of Spy Kids and Sin City fame) has the kind of pull in the industry to convince the men in suits that a movie thought up by a kid is a viable proposition.

More fool them.

What The Adventures Of Sharkboy And Lavagirl In 3-D proves above everything else is that studio executives view their seven-year-old audience as idiots.

Because although the film has noble intentions and emanates from a place of genuine purity, it's a supremely crass and ridiculous work of art.

The story revolves around a young dreamer called Max (Cayden Boyd), who falls into a fantasy world of his own creation where he has to battle the evil Mr Electric (George Lopez) with the help of tween superheroes Sharkboy (Taylor Lautner) and Lavagirl (Taylor Dooley).

The latter emits heat from every pore, the former is supposed to be a Tarzan-type who was raised by sharks, but is actually a hair-gelled golden boy wearing a silly rubber fin on his back.

There's also a rather obtuse subplot about Max's parents, played by David Arquette and Sex And The City's Kristin Davis, if you can be bothered to sift through the narrative muddle.

Director Rodriguez has made his name for doing everything on his movies and this is no exception, with his name appearing multiple times on the credits.

The downside to his hegemony, however, is his complete lack of perspective.

Aside from the shoddy excuse for a plot, the movie looks terrible, the 3-D barely registers and the acting often errs towards the wooden.

Missing the vivacity and fun of Spy Kids (Rodriguez has already started ripping off himself), this is a garish, amateur spectacle.

Aimed squarely at children, it fatally misfires on all counts - alienating both the adult chaperones and sadly proving too trite, weedy and vacant for even the most forgiving of youngsters.

Rodriguez has talent - let's hope he uses it more wisely in the future.

See it at UCI, Odeon