Argh This Sub Hunting Is Driving Me Insane!

I'm stuck on KLM mission 5 because I seriously lack the skill of depth charging. I spent an hour working on three subs without a single sinking. The subs surfaced after a while, but even after SEVERAL hits ( five or so before they submerge, only to surface again...)

I know that if the dot is blurry, it's lower than 20m, that's all I know. I need pictures on how much to lead the sub and stuff.

strange, I just beat the mission in half an hour by turning off my engines and waiting for the subs to surface, and there were only two subs...

Well first fire your charges at 120 meter with the option +10meters, after 200 meters with option +5meters, and usualy it goes fine. You can know the sub's depth with the order "engage target" of course you must choose first the sub you want to sink. And then simply input the depth.

Good hunting!