With the increase of maritime traffic, the risk of wastewater generated by ships in coastal areas has raised much attention. The present study proposes a model to estimate wastewater’s high-resolution spatiotemporal distribution, including the greywater and sewage generated by ships in coastal areas. The shipping traffic characterization in this region is presented, and the spatiotemporal distribution of the wastewater generated by ships is demonstrated. It was found that the total amount of wastewater generated by the ships operated in the whole research area during six months is 12.1 × 107 m3, in which 9.97 × 107 m3 is for the greywater, and 2.13 × 107 m3 is for the sewage. Passenger ships contributed 83% of the total wastewater, while cargo ships accounted for 12%. The amount of monthly wastewater is not only varied over the total amount, the spatial distribution was also changed as the shipping activities are different in different months. The model presented in this study increases the spatiotemporal resolution of the wastewater generated in the research area and can distinguish the contribution of different ship types to the total amount of wastewater. The results can optimize the wastewater collection strategies and better design the collection facilitates in the research area.