Kennedy was interested in naval warfare. He wrote and presented a substantial number of television documentaries for the BBC on maritime history in the Second World War, beginning with Scapa Flow, followed by the dramatic narrative of the sinking of the Bismarck in which he was involved. Other subjects included the U-boat war, the story of HMS Belfast, and the Dieppe Raid and St Nazaire Raid. "The Life and Death of the Scharnhorst" (1971) brought him into contact with survivors of the battlecruiser that had sunk his father's ship "Rawalpindi". The series included "Target Tirpitz" (1973), a history of the extraordinary attempts to sink the feared German battleship; two of the films led to books.