It is a decision that will lay chittering tick eggs in Lou Gossett's nightmares until the end of his days, and the shark totally did that shit on purpose.
Which, of course, is something a shark wouldn't do. Which leads into the second point ...
The Shark Is a Creature That Cannot Possibly Exist
The villainous shark at the center of Jaws 3-D is formidable enough to smash its way through an entire amusement park before getting stuck in an underwater DJ booth like a cat with its head in a Pringles can, but the beast's physical strength isn't what makes it so terrifying. It's an animal that confounds both science and nature, like a stack of physical impossibilities somebody stapled together to cheat on a biology test. The shark is an animal that should not be. You'd need crisis counseling just for making eye contact with it. It's as if it were ripped from the darkest corners of the human psyche, straight from the oozing puddle of corrosive blackness in everybody's mind that incubates our greatest fears -- specifically, the age-old fear of being eaten alive by a big ugly fish.
First of all, the shark is 35 feet long, which I think technically makes it a sea monster. We never find out where it came from or why, out of the entirety of the world's oceans, it suddenly decided to imprison itself within 200 acres of South Florida theme park. It swims backward, which is impossible for fish. It has enormous Jon Heder gums, and it snarls, which is something that an animal without lungs simply cannot do.
It also has some serious meth teeth.