A group of mourners and a man spat from the depths of Hades build a boat from the debris of New Orleans to rescue their lost loved ones trapped beneath the sea.
When the body of a man is found completely destroyed in the swamps in Louisiana, the medical investigator Sam Rivers is assigned to investigate the murder. He travels with the biologist Mary Callahan to the location where the victim lived in a floating house and he meets his family and friends. They find that Chinese snake-heads genetically engineered that belong to a wealthy hunter are attacking and killing the locals. While the group fights to survive, the hunter Jeff arrives with his team to hunt the predators.
Open on gorgeous swamplands of the Atchafalaya Basin in the summer. Lots of beautiful teens are at the beach the weekend before Gator Fest. That night an animal smuggling deal goes wrong and a large sea creature escapes into a swampy backwoods river. At the McDaniel's "Gator Shack" restaurant, a local, Jackson is drunk, and gets mangled to bits. The town sheriff blames the carnage on the McDaniel's "escaped" pack of gators and tries hauling them off to jail. Rachel McDaniel, head of the family, claims to have seen the fin of a shark! Rachel and her family, along with the help of a mysterious stranger, Charlie, take on the Swampshark and the law to clear their names, save Rachel's kid sister Krystal and prevent the unwitting folks at the upcoming Gator Fest from being torn to shreds by a beast the likes of which no one has ever seen!