The Mediterranean Sea is a semi-enclosed basin displaying an active thermohaline circulation that is sustained by the atmospheric forcing and controlled by the narrow and shallow Strait of Gibraltar (SoG). The main goal of this chapter is the investigation of the effects produced by certain specific factors on the simulated hydraulic behavior of the SoG by the nonhydrostatic assumption, the resolution adopted, and the parameterization used for mixing on the simulated hydraulic regime. The chapter is organized as follows. After an introductory section, two models (Princeton Ocean Model (POM) and Massachusetts Institute of Technology general circulation model (MITgcm)) are described and validated in the second and third sections. The comparison of the models in terms of the simulated internal wave field, three-layer properties, and hydraulics is shown in the fourth section. Conclusions are discussed in the last section. © 2014 American Geophysical Union.