: well what i meant is JUST the underwater section, take the whole volume cut
: it at the waterline and discard the rest. At that point the volume
: centroids are the same....

Perhaps in an idealized situation, with a hull that has no thickness, and is the same density as water. Otherwise, the thickness of the hull itself, particularly along the keel line, would create a slight difference between the center of gravity and the center of bouyancy.

Consider too, that if you were to remove the amount of the boat which is above the water line, then the remainder so the boat will not need to displace the weight which was removed. So what is left, if allowed to float (or sink) by itself, would have a different displacement. If your hull materials are not as dense as water there is more above the surface for you to cut off. Do that and the process repeats itself.

PGJ