I just got done watching HFRO last week. No torpedo explodes on a CM.
And what you should have done was get really SHALLOW. You are much harder to detect because of 1) ambient wave noise, and 2) Active can't detect you very easily at shallow depths (ie. periscope depth) from afar.
and for your blow-tanks monuver. Yes, it can be done (I have done it.) But you need to be going really fast, and need to be at a reasonable depth. As I recall, the waters in that mission aren't very deep. Best thing is about 100meters, flank speed, with the torpedo coming at you from ~45 degrees off your bow. Don't go too deep or the Torp will curve in the vertical and hit you from below.
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