It depends on a number of factors and weather I absolutely HAVE to engage. If the waters are calm, I'll fire a magnetic fish under his keel in hopes of breaking his back.
Like this...
If the water is rough, use contact and a good 90 degree aspect from the target to maximize your chances of a hit. DO NOT STAY TO WATCH THE FIREWORKS. DIVE DEEP as soon as the fish leaves the tube, I usually head down leg of the DD's path (so if he's on a bearing of 000 I'll turn to bearing 180) which means the speed in which you part is doubled by the fact you have a while before the fish impacts. Usually a hit on a DD will sink it so you only have to worry about missing. Something thats very possible if your using OLC's GUI like I do! "I'm sure I calculated the AOB right..." "Herr Kaleun! Wasserbommen!"
