The sub service was not very aggressive early in the war. As peace time commanders were replaced with hard nose skippers things got going. USS Wahoo, USS Tang and others took a heavy toll in spite of faulty torpedoes and alerting the Japanese to the boats diving capabilities by idiots in Washington. Service in subs took a different sort of mindset, especially in our diesel boats. RIP Grayback.
Well, the early POS torpedos would not detonate, so why risk going in hot just to watch duds and then get the hell depth charged out of you?