Titans of the Deep (1938)

Prominent scientists Dr. William Beebe ('William Beebe') and Otis Barton (Otis Barton), using the Bathyspere invented by Barton, descend several thousand feet to the ocean floor off of the shores of Bermuda to study and film sea creatures seen and filmed at that depth for the first time. A sometimes staged semi-documentary that was often sold and advertised as an exploitation/horror picture.