This module starts with the basics of Chapter 4 of the MARPOL Annex VI. It focuses on energy efficient operation of ships and increasing energy efficiency of ships during design. Ship resistance components (viscous, wave-making, air and appendage) are discussed as well as their reduction ways. Increasing propeller efficiency and improvement of propeller-hull interaction are examined from an energy efficiency perspective. A tutorial is also provided to assess the impact of resistance and propulsion improvement methods on fuel consumption.