HMS Seadog (P216)
 HMS Seadog was an S class submarine of the Royal Navy and part of the Third Group built of that class. She was built by Cammell Laird & Co Limited Birkenhead and launched on 11 June 1942. She previously had the pennant P216. So far she has been the only ship of the Royal Navy to bear the name Seadog.She spent most of her wartime career in the Far East except for a brief spell in home waters off the Scandinavian coast where she sank the German transport ship Oldenburg.