The objective of COMPLETE project is to minimize the transfer of invasive aquatic species. One practical goal of the project is to demonstrate the effect of hull cleaning on ships’ performance and provide data for shipping companies to optimize the intervals of hull cleanings. The study is based on a theoretical framework containing physical initial values, through which the shipping companies are able to apply the results to their fleet. The selected framework has been implemented by conducting empirical measurements and data collection during several sea voyages. Exhaust gas emissions, fuel consumption, trim, draught, rotation speed and pitch of propellers, shaft power and ship running speed were recorded. The prevailing weather data was collected from the meteorological institutes. With these recorded values, while taking into consideration the performed interval of the hull cleanings, the decrease in the ships’ efficiency due to biofouling can be calculated for each examined ship.