Climate change and anthropogenic impact have greatly disrupted the state of the marine ecosystem. Because of their explicit importance in global economic processes, it is generally necessary to conduct ongoing surveys to determine the status and early detection of changes in the marine ecosystem. Different sea testing and sampling techniques are possible, which are divided into three main categories: destructive (using fishing gear), non-destructive and combined methods. Many methods can be very destructive, for these reasons the underwater visual census (UVC) method is the most used method that falls into the category of non-destructive methods. In our research in the Martinska Bay in front of the Department for Marine and Environmental Research of the Ruđer Bošković Institute, the underwater visual census technique was chosen using the transect method. A total of 47 organisms were identified, of which 14 are fish species, 22 invertebrates and 11 algae. In all four conducted visual censuses, the species common two-banded seabream (Diplodus vulgaris), Mediterranean sand smelt (Atherina hepsetus), painted comber (Serranus scriba), golden goby (Gobius auratus) and brown comber (Serranus hepatus) were recorded. The most numerous fish species was Mediterranean sand smelt (Atherina hepsetus), followed by the salema porgy (Sarpa salpa) and the mullets (Chelon auratus, Chelon ramada). All three species make schools. In further research, it is necessary to perform long-term monitoring to determine the distribution and to investigate the interactions of fish species with the habitat.