When Renat invited his friends to relax on a yacht in the Mediterranean Sea, he could not even imagine how it would turn out... It all started when he, Ilya and Nastya discovered an abandoned coaster. It contained diving equipment and... many valuable artifacts from the Second World War. Who raised them from the bottom of the sea?.. Suddenly the owners of the ship, the Germans, appear. Two members of their crew died while exploring a submarine that sank there. At first they look like ordinary treasure hunters. However, when news arrives that the granddaughter of Baron von Kracker has been kidnapped, friends begin to realize that these people are hiding something. Who are they - simple adventurers or real “black divers”?