Canada's last working sub?

[Ironside]

Interestingly, old diesel submarines can be harder to detect than modern nuclear submarines. The reason being that a diesal sub can turn off all of its machinery and run completely silently off of batteries. A nuclear sub can never shut off its reactor and as such can never completely eliminate its noise signature.

In some situations low-tech is better.

Could explain why the US is training vs Swedish diesel subs (with Swedish crew, rented ). Seems to be needed according to what has been mentioned here.