Nowadays, Niteroi is considered the city with the best conditions of basic sanitation in the State of Rio de Janeiro. Despite that, Niteroi constantly lives with its beaches being classified, regarding the conditions of bathing, as unfit for recreation of primary contact, even after the implantation of the submarine emissary of Icarai, which assesses the disposition of the sewage collected from eight districts of the city. Thus, the objective of this work is to analyze the evolution of bathing conditions of the beaches of Niteroi, close to the submarine emissary of Icarai, and to identify the main factors that influence these conditions. For that, the following was performed: (i) a qualitative study of Guanabara Bay conditions; (ii) the effects of the disposal of the sanitary effluents by the submarine emissary; (iii) a statistical analysis of the bulletins of the beaches studied; and (iv) a correlation between the rainfall index and the bathing conditions. Through the studies carried out, it was verified that the sanitary sewage arrangement carried out by the submarine emissary minimally impacts the bathing conditions of the nearby beaches. On the other hand, due to the streamflow of the Guanabara Bay, the pollution irregularly disposed of by other cities around the Bay is responsible for bringing to the shore of the Niteroi beaches contaminants that directly interfere with the beaches' bathing conditions. It is important to note that Guanabara Bay receives the drainage of 55 rivers, of which t50 are considered completely polluted by sewage. Another factor that impacts the bathing conditions of beaches is the pluviometric precipitation index of the locality that, because of the high levels of seasonal precipitation, surpass the capacity of collection and treatment of the sewage treatment stations, causing the overflow of this sewage to the ocean.