This study investigates the behavior of a positively buoyant jet from a single-port discharge using both numerical and experimental approaches. Shortly after discharge into the sea, a buoyant jet reaches the surface, potentially having a significant impact on the local environment. We evaluated the use of downward-inclined nozzles as a solution to enhance flow trajectory and dilution up to the surface. The discharge process was numerically simulated using OpenFoam, with nozzle inclinations of 0 and -15 degrees, to explore the inclination effect. OpenFoam which is an open-source software for CFD simulation, was developed to facilitate the modeling of complex hydrodynamic processes. The simulated scenario was experimentally validated using a laboratory-scaled model of the horizontal discharge in front of the Laser-Induced Fluorescence (LIF) system for various discharge densimetric Froude numbers (〖Fr〗_d=10, 15, 20). This setup was used for the capture and analysis of jet trajectory and dilution along the flow path. Comparing the numerical results with experimental data demonstrates that the model can predict geometric characteristics and dilution with reasonable accuracy. Once calibrated, the model has been used to predict flow features from the inclined nozzle at -15 degrees. For the -15-degree jet, the dilution rate at the sea surface was found 18.72% higher than the horizontal discharge. Downward inclination directs the flow in the opposite direction of the effective buoyancy and it leads to a longer path and better mixing. Therefore, our results show that to what extent the inclination of the nozzle will affect flow mixing and dilution at the surface of receiving water in coastal sewage disposal.