À couteaux tirés (1964)

Via Something Weird: "Four men representing the world’s great criminal organizations unite to locate a cache of sunken treasure. The treasure is in fact a fortune in diamonds and secret documents that was lost by the Germans in the seas off Monte Carlo during the war. Following their every move are representatives from every secret agency in the world, amongst them, the British, the Russians, the Germans, and the Americans, all seeking the important papers contained within the treasure."