The Secret of Two Oceans (1955)

The enemy agents from an unknown nation have secret automated facilities set up in the Atlantic and Pacific oceans for the purposes of sinking ships The super submarine Pioneer and its intrepid crew is dispatched to find the source of these mysterious sinkingsUnknown to the captain his chief engineer is working for the bad guys intent on stopping their efforts at any costIt seems the real chief had a twin brother who was a circus acrobat who murdered and replaced him