Improving the hull form. Improving hull coatings. Reducing bottom friction resistance. 3. Improvement in propulsion efficiency. Modifying propeller. Install energy-saving appendages. 4. Improvement in the main engine s efficiency. Change and convert the main engine. Recover waste heat. 5. Reduction of hull weight. Improve steel materials used. 6. Use of alternative energy/ fuels. Use wind or solar energy. Use of LNG.