Dock Water Allowance
When a vessel moves from salt water to water of lower density it will increase its draught. The amount of change is known as the “dock water allowance”.
The water density is measured by an instrument known as a hydrometer.
The formula for calculating dock water allowance
DWA Doc water allowance(in mm) = FWD Freshwater Allowance(in mm) x 1025 – (measured dock water RD)