What Lies Below (2020) on Netflix

Plot summary

At her family's lake house, sixteen-year-old Liberty Wells, called Libby, is back from summer camp when her mother, Michelle, a romance novelist, introduces her boyfriend, John, an aquatic geneticist who says his work helps creatures adapt to changing environments. John gives Libby a bracelet marked with the symbols of a fertility goddess. That night Libby walks into the kitchen, hears moaning, and retreats to her room, where she finds John standing in her doorway and pretends to sleep. The next morning she and Michelle unearth old time capsules in the yard and quarrel; Michelle says she felt unwanted by her father. A centipede bites Libby, and John tends to her. Then Michelle becomes ill and tells Libby she has accepted John's marriage proposal.