Thank you all. Really usefull tips :) .

You still can kill a KM sub. You have to wait for it to take a bait or get into a really
good position.

That monty can take a few proxy torps for you to get on top of it anyway.

There's really two different tactics to use vs subs depending on which nation you face.

If it's not a KM sub, use a boat with high cruising speed and maneuverability to dodge
it's torps, get on top of it and DC it. If he goes deep, just circle. He can't escape
you now!

If it's a KM sub, do not approach or their special 'proxi' torps will sink you. Dodge as
well as you like, it won't help. Instead once you have the sub on sonar, track it and
mention it on your team chat to be sure your team's big ships know exactly where it is.
Then just wait for it to surface and try to shoot it once or twice before the BB's all
turn their guns on it at once.
;)

Real Sub hunting is with DCs.

It's also all in LK's guide. And the best way to know how to kill one is being one, so you
will understand what that sub is thinking. It's a lot about dodging and positioning. And
the best subs to hunt are HEIs, SS1s, and S types lol.

I actually used AA guns once for the lolz when I was sub hunting. all they saw was an FF
trying to shoot down a scout lol.

If you have plenty of credits to burn, get a CL with LOTS of gun mounts, load it up with
HH and auto FCS, and PEW PEW!

If you don't have plenty of credits but still enjoys the pure satisfaction of sinking
subs, load depth charges, and read LordKelvin's guide on ASW in USN section.

While US centric, LK has a good guide on this.
http://www.navyfield.com/board/view.asp?Num=136777&Sort=A01

The escort frigate with a sonarman can be a good idea even if you're in a DD/CL. Being
able to sometimes OH without losing sight can be very useful. Also, it expands your sonar
coverage area.

<3 my towed array. Except when it crosses me or a friendly. >_>

1 - Make sure you read up on dodging torpedoes as well. Except for proximity torps,
proper torpedo dodging will keep you alive long enough to use depth charges.

2 - Make sure you carry a sonarman in your support slots if you're running a FF, DD, or
CL. Even a ship that doesn't need one will benefit from a larger detection radius by
having even a low level sonarman.

3 - If you're a larger ship, drag a frigate-with-sonarman along with you as an escort.
The escort AI is a little annoying, but the sonar is worth it. Even if you can't shoot
the sub, you can avoid him and make it harder for him to make the kill.

4 - Until you're well practiced with hedgehog aiming, you should use them on gradual fire
to avoid wasting your entire salvo with a miss. Hedgehogs are also a huge credit drain,
so use them sparingly or they could prevent you from getting your next ship!