The subject of this graduate paper is the reconstruction and upgrading of the Črni mul harbor in Crikvenica. The aim of reconstruction is to get as many as possible quality and protected mooring places. The graduate paper involves two variants of the solution the harbor Črni mul. A detailed technical description is presented in this paper, an extension and dimensioning of the primary breakwater is constructed, the construction of a new built secondary breakwater, a new coastal wall on the breakwater and the mainland. Harbor, Črni mul, capacity is 135 smaller vessel partly located in aquatorium of harbor and partly outside of the aquatorium on buoys. This reconstruction and extension predicts the mooring places for vessels from 5 to 12 meters in length and a maximum depth for vessels of 1.85 m. In both variants it is provide to remove the existing gutter and wooden grid as well as deepening of the shallow waters of the communal harbor to a depth of -2.2 m to -2.4 m. The aquatorium harbor in variant 1 is divided into 2 pools and has capacity of 128 vessels, while in variant 2 the port aquatorium has 3 pools with a capacity of 157 vessels. The first variant solution predicts filling and spreading the operational shore of the communal harbor for 12 meters, resulting in a new 1,639.50 m2 operational land. The aim of this graduate paper is to get a protected harbor during the year with as many quality and safe mooring places as possible with preservation of the ambient space value.