How much danger would we get in sh-4

[oscar19681]

As i understand it the japanese did not have a very good asw capabilaty . What was the biggest threat to us-subs in the pacific ? I liked sh-3 because just about the whole world was after your sub . Arent the japanese destroyers a laught to sneak away from? I know everything about the u-boat war . But i no very little about the situations the us subs had to face can someone fill me in?