Dealing with a warship

[Scarredclown]

near Honshu, i was chased by a warship (cant remember the class, will take notes next time). The sea was pretty rough and he was not having great success at locating me. I try to get a good shot at him but all my torpedoes miss. His movement were erratic. Should i not bother trying to get him at all ? What would have been a god firing position in that case ?