Cody

I am on the chapter with the ship where you have to kill the capt. and get the submarine card. I am almost certain I have killed him, but it keeps telling me to find the ship captain and get the submarine card. I have like 3 cards already, have searched the ship[ from top to bottom and cant get on the sub. I freed the prisoners too. I am about ready to quit, been trying this for 3 days and cant get out. Where is this capt at? I know I must have killed himk killed him.