So two mermaids walk into a bar. If that sounds like the start of a joke, it is, albeit a sick and sinister one. This 2015 Polish film follows two sister sirens who befriend a rock band and follow the musicians back to a seedy nightclub. There, the mermaids sing for their supper. The trouble is that supper in this case just happens to be humans. Lavishly choreographed musical numbers strike a queasy balance with gruesome scenes of mermaid feeding.