Overall, I'm sure your right there, Jeff519 ( and welcome to SH3 forums, BTW

)
There are many areas in the North Sea and, even worse, the Baltic Sea!!, where a submariner couldn't ever expect any comfort from Thermoclines.
However, U-Boats operated in many areas where these distortion effects would have come into play.
Nowhere near as much as the Pacific though, but I think Thermoclines
are modelled in SH4??