This movie is truly worse than awful. It's crying out for MST3K treatment. It's so bad, Rocky Horror Picture Show looks good by comparison. The plot sucks, the acting sucks, the special effects suck. I mean, in one scene, people are in a H3 and a girl goes, "There's sharks swimming in the street!". Camera shows her viewpoint as you see a bad CGI fin go through the water (with no ripples or wake). The immediate next scene is them driving away on a road that has less than 1/2 inch of water on it.
It doesn't get better, it just gets worse. Some points are so bad they're funny, like the guy shooting sharks dead while the tornado is flying them in the air - with a revolver. Some scenes are dark and raining, and the immediate next scene has sunshine.
This movie isn't even good enough to become a midnight cult classic. Good thing it was a free "rental".