Actual Weight vs Displacement Weight
Any boat (or anything, for that matter) that floats will displace it's weight in water. The "actual weight" and the "displacement weight" are the same number. And, as stated before, salinity doesn't matter. 5000 lbs of salt water weighs exactly the same as 5000 lbs of freshwater, or even 5000 lbs of feathers for that matter.What will change is the boat's actual displacement. As you put things in it, it will displace more water. Usually, when a mfg refers to a boat's displacement, they're talking about the "dry displacement", no fuel, no water or waste, no add-ons.