In the final stand-off with the Cuban Coast Guard jerrycans are shown being taken out of the boat. At this time jerrycans were still a German product only. The only ones in non-German hands were those captured by Allied forces. later they were copied by the British & US military but its highly unlikely they would be in the hands of backwater sailors like those depicted until after the war.
When the boat is slowly cruising up the river in Cuba looking for refugees, a crew member's hand can be seen moving tree branches away from the camera.