Which is exactly what I said in laymens terms. I'm a bit confused on how your statement contradicts my statement, unless you just couldn't resist the need for an early morning jab with no basis? You basically said the sameexact thing, you can weigh the ship and divide by the density of water to calculate the displacement . "Volume of Displaced Water = Weight of Vessel divided by the Density of Water Given any of the two variables above, you can solve for the third. " Pacblue I do a lot more in this industry than just drive yachts. My initial statement: "Displacement is measured in volume of water a ship displaced, in order to get (derive) the weight of the ship. Obviously nowadays, they can weigh the ship. By weighing the ship you can work backwards and get the displacement value." Work Backwards= is laymens terms for calculate, if reading comprehension is not your strong suit. And since the density of water (either fresh or salt, you choose) is a constant, you can calculate the displacement with just the weight and choosing what type of water the ship is displacing to get both the displacement values in freshwater and saltwater.