Xtinction: Predator X (2010) on Netflix

Plot summary

Laura Le Crois has been away from her Louisiana swamp home for twenty years. Her father, Pappy, has gone missing along with other locals, so she comes back and keeps the family boat tours running. The town is not as she left it: Pappy owes the bank, her old boyfriend Tim Richards is the sheriff, and her ex-husband, the zoologist Charles LeBlanc, is buying up swampland. A young man named Matt asks Laura to take him and his girlfriend Mandy on a sunset tour so he can propose to her, and she agrees. They set out on a small motorboat. Deep in the wetland that evening, two men dump a body into the water in front of them, and something in the water feeds on it.