Jap subs hard to kill!

[Tim Stan Armstrong]

Found a japanese sub sitting in harbour on my last patrol, hit it with a torp expecting it to sink fairly rapidly, nuthing happened so i waited for 30mins or so and hit it with another and another, still it has'nt sunk!:hmm:

So i gave up, three fish on a sub is a bit too much.
Im using TMO RSRD and NSM

Maybe a bug or are they just eye candy and not meant to sink?

Thanks.