A synopsis of the film "Underwater Stalking" translated from the German. Note the dates, this film predates Cousteau's first spearfishing film, although the hunting here is given less prominence.
Shot in 1940 with a 16mm Zeiss Ikon Movikon K16 camera in a self-made, waterproof case in front of Curacao. The strip was released by the UFA Berlin. In this partnership was Hass cameraman, actor and comment speaker, the design was taken over in 1941 by UFA director Rudolf Schaad. In order to give the underwater shots from the Caribbean a corresponding frame and to have more intermediate cuts available, was nachgedreht 1941 in Berlin, Vienna and Dubrovnik (camera: Karl Kurzmayer): In the Viennese Krapfenwaldl-Bad was a frame plot with the Austrian actress Helli Servi, which should prepare the audience for the unfamiliar underwater shots. In an aquarium in the film studios in Babelsberg intermediate cuts were made with the help of back projections, showing Hans Hass and his friends with their underwater cameras and hinted stitch scenes. At Dubrovnik, additional cutting material was shot above and below water. Among other things, a scene in which Jörg Böhler dives with a spear in a wooden boat. While staying at Dubrovnik, Hans Hass tested new underwater cameras with Plexiglas housings and photographed in color. Some of these shots can be seen in his book "Photo Hunting under Water" (1942). On May 8, 1942, the premiere was in the Ufa Theater Tauentzienpalast in Berlin. He ran there as a pre-film to "Violanta" by Peter Ostermayr and in the aftermath as a prelude to the newsreels.
and here is the move "Pirsch unter Wasser"
The clarity of the movie is astonishing, although not a lot of it shows actual hunting, but considering the date it is breathtaking in the quality of the images.
Note the underwater weapon is a polespear with a breakaway tip that connects via a line to a reel on the butt of the polespear, you can see the reel or line drum in one of the photos of the diver pausing just below the surface as he surveys the hunting opportunities below.