Eden Lake

Eden Lake is a 2008 British horror thriller written and directed by James Watkins and starring Kelly Reilly, Michael Fassbender and Jack OConnell.

After breakfast, as he is determined to report the unruly kids to their parents, Steve stops at a house hosting a group of bikes he thinks belongs to the kids. With zero response at the front door, he commits forcible entry, and he narrowly escapes out of a window before the homeowner, the father of one of the teenagers, returns. The couple quickly head back to the lake. There, Steve goes scuba diving and Jenny sleeps on the beach shore. Once Steve gets back from the beach, however, he realizes their beach bag containing his car keys, phone and wallet have gone missing. Instinctively, they check on the car, but it is gone. Returning to town on foot, they avoid collision with their car that is being driven recklessly by the gang through the woods, only stopping for gang leader, Brett Jack OConnell, to smirk at them.During a confrontation with the gang at nightfall, Steve demands the return of his belongings which Brett acts in denial about. Once Steves phone sounds off in Bretts pocket, a scuffle ensues leading to Steve mortally wounding Bretts dog with the gangs produced knife in the heated situation. This fuels Bretts lust for revenge after returning their car keys. Brett and his gang proceed to go after the couple, smashing their car windshield and headlights with rocks. Steve and Jenny are able to get free from a steep slope before eventually crashing into a tree branch. Steve, stuck in the branch that came through the windscreen, urges Jenny to run for help and she escapes, finding a place to hide and spend the night. ........

Source: Wikipedia