Our buddy Werner said it all.
"Yup, the thermal layer (thermocline) helps in damping the sound of your boat. It also helps a lot more if the seas are rough too"
It dampens. Not hides your sub as a cloak in Star Trek universe. And also remember, bad weather is your friend. They always will have a bad time trying to find you. That beautiful blue pool that sometimes the Pacific (hence the name) becomes sometimes is only good for cruise liners

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Edit: I was going to do some videos on escpa tactics from Destroyers. I Hope sometime I'll have time do to them.