During an adventure holiday on the Belgian coast, the Helden soon turn their residence in the dunes into a mini-amusement park, including a high-speed rollercoaster. The summer can't go wrong. Something even blossoms between Dempsey and Eva, a girl also staying by the sea. But their romance is short-lived, as Eva has to leave for a language camp in England. The Heroes comfort Dempsey and decide to go after Eva, across the sea in homemade boats! But when they set sail, things go quickly wrong.