[Nuoz]

I am playing in 85% (contact updates on,100% in GWX for some reason) I only use the contacts update because its enormously time consuming to manualy plot and very difficult to get an accurate range with the periscope/UZO.. Although, this means no instant id of a target, no AoB, no speed. Just a generic description like destroyer, patrol ship, etc if you get a visual or warship, marchant if you are using your hydrophones. If i wat to shoot i need to enter the time of shoot distance (range), calculate the AoB for each target, Jim's tools (included in stock and GWX) will only help you calculating the AoB if you are aprox 90 of an incoming target.
Then you need to plot, count one minute at least and plot again for a speed value (using the charts). Real life Captains and people who really go 100% still have to plot and calculate AoB based on aspect ratio and whatnot. Its very risky and prone to fail letting a valueable fish go at a 35knots incoming destroyer. I never shoot at escorts or destroyers.
AoB, range and speed may not be important if the destroyer is coming towards you at 0º or 180º but mind the fact torpedos need 300m to arm. And the very shallow chance you have to hit an incoming bow. Maybe magnetic fish would prove better at this, but still very risky and bear the 300m to arm. Do the enemy sub hunters zig zag? I remeber that was a mandatory tactic for any human playing a DD (Destroyer Command) against human U-boats, SH2.
My point is, if you play 100%, in shallow waters, upon detection your only hope is to flank and manover until you can dive deeper.Its often better in my experience to even avoid diving for a couple minutes to gain some more ground, until the splashes in the water hit your watchmen.