The notoriously bad-tempered Karl Kruse is the lifeguard at the local outdoor pool in Grubberg. As grumpy as he may be, the swimming pool is nevertheless the center of his life - he has been keeping things tidy here for 30 years. The mayor, on the other hand, is unhappy with the aging pool and would like to close it down. Dengler, the construction tycoon, promptly senses an opportunity to get his hands on cheap building land for expensive apartments. But the two of them have done the math without Karl. In order to save his beloved open-air swimming pool, he initiates a petition for a referendum, for which he needs at least 600 signatures. But it's not easy for him to get them, because the bossy poolside sheriff is not very popular with the few remaining bathers. Karl's only real ally is Nigerian refugee and lifeguard trainee Sali, who, however, dreams of moving on to Canada. His feelings for ex-professional swimmer Lisa get in the way of this plan.