P-5M Marlin NavyMartin P5M Marlin airplane model. The Martin P5M Marlin, built by the Glenn L. Martin Company of Middle River, Maryland, was the last flying boat in service with the United States Navy and the US armed forces in general. Built as a successor to the PBM Mariner, the new hull form and new conventional tail were fitted to a Mariner to become the XP5M Marlin prototype. The prototype had nose and tail turrets with twin 20 mm cannon in each, as well as a