Thank you for your well thought reply, Philipp.
I agree that it does seem the "bobbing in a bathtub" behavior of ships has been due more to people wanting ships to be tossed about on stormy seas because that's how it looks in movies.
We are talking about a sim that is supposed to at least resemble the real world, after all.
It is a shame that SH3 will not allow a ship's mass to behave differently in the different effects of sea states, such as greater torsion and flexion in severe storms causing a ship to roll and nose under.
The buoyancy seems fine. Battleships and tankers do indeed ride very low in the water. Both types of ships are very massive and heavy.