Visiting the USS Pampanito in SF recently, I read a plaque that said, while the US submarine force in WWII formed only 1.5% of the Naval force, it was responsible for something like 55% of confirmed kills of Japanese shipping. The tradeoff was that the submarine force suffered about a 30% loss rate.
Pretty brutal odds, knowing that you have a one-in-four to one-in-three chance of never getting off that boat.
Actually, no. Submarine crews suffered the highest percentage of losses across all American armed forces in WW2. See link: