Displaced weight vs Dry Weight
Most of you know this, but in case this helps at all -
The term "displacement" as used in the boating world may have all the aforementioned confusion assigned to it, but in terms of simple physics, the weight of the water that a floating object displaces is equal to the weight of the object. You are actually displacing a certain volume of air, too, which contributes very minimally minimally to the bouyancy (that''s the way helium balloons work - the rubber plus helium do have mass, but less mass than the air the inflated balloon displaces).
So, if you add mass (weight) to a floating boat, it has to sink lower to displace an equivalent amount of water weight. If you remove mass from the boat, it has to float higher and displace less water. That''s the only way equilibrium can be maintained.