Nautical tourism is increasingly popular in the Republic of Croatia, and the potential of its development on the Croatian coast is recognized all over the world. Thanks to the natural beauty, the indentation of the coast and the diverse offer of activities at sea and on land, the number of visitors increases every year. Sustainable development is a concept that is mentioned more and more often recently, and by implementing its basic principles, we try to prevent negative impacts that arise as a result of mass tourism. In order to preserve natural beauty and other resources and enable their further exploitation by future generations, sustainable development measures and strategies are followed. Economic, social and ecological aspects of sustainable development are closely related to each other, and it is very difficult to focus on just one of them. This paper analyzes the implementation of the principles of sustainable development on the example of the company ACI d.d., the largest chain of marinas in the Republic of Croatia, but also in the Mediterranean. ACI d.d. as a leader of the green transition, recognizes the importance of preserving the sea and the environment for future business and implements various measures to achieve sustainability.