The lost German U-boat

A secret Second World War mission, with two German submarines bound for South America, falls into disarray when one of the subs runs aground on a deserted island in the Atlantic Ocean. The crew hide the boat under foliage but also leave the top-secret cargo on board. The other sub heads back towards Europe but soon runs into trouble. 
Many years later, thirteen young men, recent school graduates, decide to buy a boat and after long preparation and practice set off on the adventure of a lifetime. After night spent partying with some young women on a desert island, they come across the hidden sub and decide to investigate. 
From that moment on, their lives change, and their carefree adventure leads them into real danger.