Displacement (Δ)

Displacement $\Delta$ is the mass of water the floating hull displaces, equal by Archimedes to the ship’s mass at equilibrium, so $\Delta = \rho \cdot \nabla$ with $\rho$ the water density (1.025 t/m^3 seawater, 1.000 freshwater). Reported in tonnes, it is the base quantity from which deadweight ($\Delta_{loaded} - \Delta_{light}$) and every hydrostatic coefficient derive. The same volume displaces less mass in fresh water, the basis of the fresh-water allowance on the load line.