Did using pure oxygen in a torpedo mean it couldn’t be detected?

Because there was almost no bubble trail, it would be much harder to detect the kerosene/oxygen torpedoes but not impossible. Torpedoes made a lot of noise. Still, it seems unlikely that it would have been detected in time to avoid being hit.

Bioluminescence along the torpedo track may have also been detected at night. That too may not have been noticed soon enough to avoid being hit.