The Russian supercavitating torpedoes are powered by liquid-fueled rocket motors. It’d be interesting to see how that mode of propulsion could be scaled-up to work in a manned submarine, considering the amount of fuel it would have to carry.
Someone picked up the story and it got press, but this is all about making a Chinese version of the Russian Shkval torpedo.
IIRC, there were a few Americans busted in Russia and imprisoned for tracking down details of this new torpedo for us.