Nautical tourism has recorded its growth in the last decade both in the world and in the Republic of Croatia. The main forms of nautical tourism are ports of nautical tourism, boat rental and sea cruises. The growing development of nautical tourism, the construction of an increasing number of vessels and ports, is causing pressure on the environment. The purpose of this paper is to explore negative effects of nautical tourism on the marine environment. Natural or attractive resources constitute the basic and starting assumption of the existence and development of nautical tourism of a particular region and country. The importance or significance of nautical tourism for Croatia is reflected in the extremely natural potential that provides it with a high position on the tourist market. Croatia has the ideal conditions for the development of nautical tourism and a series of comparative advantages compared to other competitive tourism countries. Increased demand represents a challenge for further development of nautical tourism in Croatia. Precisely because of the sensitivity of natural resources, it is of great importance to prevent the negative impact on the sea and coast, or to find a solution for the successful sustainable development of nautical tourism.