The DOBRI DUJE complex consists of a tower and a marina which form a functional unit. This study deals with the aquatic constructions of the complex, that is, the marina and the foundation of the tower, while the tower itself is the subject of other projects. The complex is situated in front of the entrance to Split’s harbor, without a direct physical link with the land, making it an artificial island which creates its relationship with the land with: • service vessels for the communication of people and goods • heliport – connection with a helicopter • underwater cables to connect to an electric grid • underwater pipes to connect to the water network • variant solution: connection to a possible future tunnel which would be a communication between the land and surrounding islands (Brač and Čiovo) The drainage of waste waters (fecal sewerage) would be solved with a purifier inside the complex emitting purified water into the sea. Also possible is an additional energy supply from alternative sources, such as sea currents, which is the subject of other projects which can be fit into the design of the construction of the complex.