If you are a child:
The boy wants to go to the Mysterious Island and The Rock takes him and they get in a helicopter with Gabriella of High School Musical and some other guy and a big bird poops on that guy and then there's a crash and they find a tiny elephant that's like a dog and now you want one of those and then a big centipede comes out and scares your three-year-old brother and he cries and your mom has to take him out of the theater and warns you to behave and don't go anywhere while she calms him down and then an old man comes along and they ride big bumblebees and The Rock bounces berries from his chest right at your face and then a giant lizard chases them and the guy with the bird poop on him falls into a lizard egg and gets slimy and the island starts to sink into the water and they find a volcano that's gold and also some giant gold rocks and then The Rock sings a song but then more water comes up and sinks the island more and they have to find a submarine and they do and they get away and the boy kisses Gabriella and now they're going to the moon.
If you are an adult:
You've got no business watching this. I'm not advocating abandoning your kids at the theater and letting them enjoy it alone, but if this were a perfect world where child safety weren't an issue, then that's what you could do and nobody would blame you for it. It's a perfectly medium-sized amount of fun for people under the age of 10 and perfectly irrelevant and ignore-able for adults. However, should you draw the chaperoning short straw, note that Michael Caine -- one of the world's most respected actors -- is in it. That's because Michael Caine likes to keep working, no matter how good or bad the project happens to be. Give him a movie script and meet his quote and you've got yourself an actor who shows up on time, knows his lines and hits his marks. Also, you'll get at least a little bit of perverse enjoyment out of watching him straddle a giant bumblebee and fly around on it because, you know, it's Michael Caine doing it.
And be warned that when it's over your kids are going to try to make their pecs pop like The Rock. It's pretty much the centerpiece moment of this film's 3D technology. He pops his pecs with reckless abandon, with gusto, with obvious pride of achievement. He even encourages other characters in the film to eat tropical island berries that he bounces off of them, saving his friends from certain island starvation by volleying the tiny fruits back into their mouths with his undulating nipples. You'll spend all of Sunday dinner reprimanding your impressionable little ones as they try to approximate this move.
And now you know.