Club Las Piranjas tells the story of Karl-Heinz, a filling-station attendant, his family Herta, a retiree, Kurt, a drugstore branch manager, and Margot, a divorced man-hunter. They all have one thing in common: they have booked a holiday at Club Las Piranjas to relax from their nerve-racking occupations.
However, their plans for a peaceful vacation are thwarted by three individuals who are determined to prevent them from enjoying their time at the club. The two animators, Edwin and Biggy, have their own agenda and do not allow any amusement outside their plans. Additionally, the always drunken club chief, Mrs. Wenger, is solely focused on avoiding any complaints from the travel agency.
Despite the scruffy condition of the Club, including issues like no water in the pool, and the mysterious activities involving Biggy and Edwin, the vacation quickly turns into a horror trip for the guests. Their only goal becomes to leave the club as soon as possible.