“Mississippi River Sharks” (*1/2 out of four) was a silly time-waster about a group of sharks who set their sights and appetites on a local Mississippi fair in which a television actor (a bewildered Jeremy London) and local news crew are attending. It’s pretty depressing that “Jaws” was 40+ years ago and featured more scares and style (and better acting) than these onslaught of recent shark movies. London is blank as usual and probably would have fared veteran taking part in another round of “Celebrity Rehab.”