I liked the movie, if it's on tv I'll probably watch it.
But,
It had some massive plot holes.
Why do the people lock Kevin up for being a mutant?!
If the whole world is underwater wouldn't people with gills be like the best thing ever?!
Also, we're told that the little girl with the map on her back can't swim.
WHY CAN'T SHE SWIM!?
In this world swimming is more useful then walking. Why didn't someone teach her how to swim before?!
That's insane!
Also, like Jim mentioned, what's the use of the dirt?
Still, it's one of those "don't mind the details, just watch" movies, and they're awesome from time to time.