Indeed - we're fortunate that their naval doctrine regarding use of submarines was a bit on the timid side. They could've hurt us much worse if that doctrine had continued to evolve and become more aggressive.
IIRC, the Long Lance was harder to spot in the water, too, because it left a less visible wake than most other torpedoes of the era.
The Long Lance was surface launched, the subs had a different torpedo but it was damn good too.