Philadelphia Naval Shipyard
On 8 February 1964, "Sea Owl" commenced a five-week availability at the Philadelphia Naval Shipyard followed by participation in Exercise "Long Hook" with joint forces of the United States, British, Canadian, and Dutch Navies and in Exercise "Canus Silex" with Canadian and United States Naval forces. In September, the submarine participated in Exercise "Master Stroke" and Exercise "Canus Slamex" with United States, Canadian, and British forces and returned to the Philadelphia Naval Shipyard on 2 November for a five-month overhaul.