Prey (2019) on Netflix

Plot summary

Toby Burns is a high school senior in therapy after the murder of his father. His therapist suggests a behavioral rehabilitation program that sends participants to a remote tropical island where missionaries once worked, leaving each of them at a separate spot. A supervisor named Kay promises to collect everyone in three days. Toby's camp on the beach goes badly from the start. Monkeys take his food, he cannot get a fire going, and a tribal mask in the water cuts his foot. Vomiting and dehydration follow, and he becomes aware that he is not alone on the island.