sit tight, when you are sure there are no enemy boats about, order a 'surface the boat' with the "S" Key, when clear of the sea floor order ahead flank and blow ballast... all of it.
If the boat appears the be surfacing stern first, order back emergency. this might help.
your only options are to blow all ballast, get the planes set for an up angle and get as much momentum as you can.
good luck
Edit: learn the following lesson from this... No target is too big to let go of. never sacrifice the boat and crew chasing a "white whale"... it takes the SH3 kaleuns a lot of deaths to learn this lesson.... in real life however you only get one shot.
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