Grant was already drowning -- in regrets, in missed birthdays, in the wreckage of a family he lost. Desperate for one moment that proves he’s still a hero in his son’s eyes, Grant makes a reckless decision and sneaks onto the Aqua Vortex, a massive waterslide shut down for maintenance. Meanwhile, exhausted maintenance workers initiate the chemical cleaning cycle, sealing the slide and flooding it with toxic cleaning materials as a powerful storm destabilizing the ride leaving Grant inside, stranded in total darkness. What follows is a gritty, claustrophobic fight for survival.