Topic of this paper is defining of underwater noise, with a special focus on anthropogenic noise, which can have an extremely negative impact on individual marine organisms and the marine environment by changing the living habits of these organisms and reducing their number in the long term. The paper identifies the main sources of such noise, such as commercial ship traffic, sonars, seismic activities, and construction activities in the sea. Marine organisms are mentioned that are extremely sensitive to certain types of such noise. The level of impact on marine organisms, and the ways in which it negatively affects their life, the change of their habitat and finally the reduction of their number, are also discussed. Some regulatory and technical measures are proposed that could contribute to improving the situation through. reducing the level of harmful effects of anthropogenic noise, considering good practice worldwide that is already applied.