Look at this
Explanation
Black and red line - behavior of sub during storm
Blue line - theoretical sea level (when wind is calm)
Orange line - difference
Now what I was thinking here...
My theory is that mass of submarine isn`t enough simulated here. As you can see on first graph, when sub is falling into water, it does not fall enough (difference between orange lines above and below sea level ).
All we can do here is that we are trying to compensate this by adding mass into *.sim files of submarine (sub gets heavier so it falls down a bit faster). But this also negatively affects buoyancy so we are loosing control at higher depths and can`t hold depth at low speeds.
I think that developers should change "mass and gravity algorythm" to simulate more fluid falling into water (under theoretical sea level) as you can see on second graph where differences between orange lines above and below theoretical sea level are not as big as on first one.
I hope you understood a bit what i was trying to explain - sub isn`t reacting too good on gravity effect (wave throws it out of water, which is ok, but doesn`t fall back as it should) that should be under theoretical sea level = it acts like "sub on rails" =
it isn`t falling into water as deep as it should and looks like it`s flying...
P.S.: Those 2 graphs aren`t exact, I was just trying to explain my theory they were painted really fast