I've found something really schocking for me:
- clear GWX (no mods including *.zon or *.som files enabled)
- Naval Academy Artillery mission (NA missions load faster than single missions so I use them for testing)
- my VIIB is on the surface, speed 0kts, all stopped
- I ordered 'Dive' and the sub went down! holy cow


what's happening? OK I was the bottom (110m)
- I ordered 'Surface' and the sub went up like a air balloon I repeat at ALL STOPPED
whats wrong with my game?? if everything's OK why people said it's impossible to sit down on the bottom?
BIG SORRY for my post describing bottoming for hours


...
edit/ I've tried the same things with submarine *.sim *.zon files from the Flavored to taste V5 modpack and got the same results bottoming with no problems.
I was always moving when changing depth so I'm really surprised with this behavior...
In the case of using the new merged prysics in IXC I wasn't able to bottom the sub cos the bow was raising instantly.
I assume that placement of the crew has no influence. Everybody in the bow but still raising.