The force of floating parts is calculater from the center of the part instead of the center of the submerged volume

The force of floating parts is calculated from the center of the part instead of the center of the submerged volume. This can result in strange and unrealistic situations, in the screenshot you can see the center of mass (the red dot) is very far from the submerged part of the craft. The yellow dot is the center of the large feul tank.
To reproduce the bug:
Build a craft with a low mass, one big part that will touch the water (in this case the big feul tank) and add some dead weight diagonally under the center of the part (in this craft this is the small feul tank). Now you can launch the put your craft in the water, you should be able to see the bug.