'Backstroke (2017)' is a short horror film about a pair of teenage runaways who take respite near a lake on their way to Florida. One of them decides it's a good idea to go skinny dipping, leaving her friend to take a solitary swim surrounded by nothing but forest... and an ominous stranger watching her from the shore. Although the piece starts off a bit wobbly, mainly thanks to its generally flat acting and its unremarkable screenplay, it eventually settles into itself (the writing and performances both improve over time) and becomes genuine tense throughout its back half. It leaves you anticipating its final reveal, which is often what determines the success of these sorts of movies, but it subverts expectation slightly so that it never feels especially predictable. It's simple but effective, with the ominous observer pretty much nailing that 'nice yet creepy' vibe that many serial killers seem to have. The back half of this is really great. Even though the ending is perhaps a little underwhelming and the opening isn't as effective as the rest of the piece, it's an entertaining and suspenseful horror short that does exactly what it needs to.