Zwei blaue Vergissmeinnicht(1963)

At the behest of their boss, London private detective Charly Biff and his assistant Ingrid are supposed to relax on a cruise along the Adriatic coast. Even before the ship sets sail, Charly gets on the trail of drug smugglers in the port of Portoroz. He soon finds out that they want to transport "snow" on the vacation steamer to Italy and sell it there. And while the other passengers enjoy themselves - and some even discover love - Charly follows the crooks' trail.