I don't know if it was changed in to the mods, but the game as is doesn't model the fact that the din of cruising at high speed submerged with the diesels on should render the hydrophone operator deaf. You can pick up sound bearings at any speed while using a snorkel. You can also go unrealistically fast underwater with a snorkel even in a non Type XXI.
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--Mobilis in Mobili--
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