Pirates of the Lake(1987)

Original title: Mälarpirater

It is the first day of the summer vacation. Jojje, Jerker and Fabian wants to borrow a sailing boat to take a boat trip so they steal it. They plan to examine all of Lake Maelaren, but a storm breaks out and the boat sinks. They go ashore, steal food and a new boat. While everybody else believes them to be dead, they have a wonderful time. They meet a crazy Count and find a dead body.