battleships are not that slow, look at WWII, how did they get battleships from Pearl Harbor to Indonesia in a year (once repairs were made). those arent even the fastest types. its true that submerged subs are hard to find, but the Allies used aircraft to find and sink German U-Boats in WWII. yes they were surfaced, but only modern subs are designed for complete underwater operation. thats why if you look at almost any WWI or WWII sub, it will have 1 or more flak gun on top.