Opportunities and restrictions of modeling of nonhydrostatic dynamics of straits of the World Ocean according to the offered classification are discussed. Straits can be subclassified on a standard basis of expediency account of the dynamic pressure in the whole area of the strait or a subdomain, guided both by common ideas, based on morphometric, hydrological and dynamic characteristics of the strait and simple criteria identifying nonhydrostatic. The boundary-value problem for the equations of momentum, continuity, turbulent closure and evolution of water constituents is formulated in an arbitrary 3D domain with two open boundaries. For solution, we use a transfer to the horizontal boundary-fitted coordinates and vertical σ-coordinate mapping the physical domain onto a computational parallelepiped with two opposite open sides. Numerical realization uses geophysical modification of a two-step projective method of the solution of the Navier—Stokes equations. Results contain an assessment of influence of nonhydrostatic on the dynamic and hydrological regimes of three allocated standard straits: Messina, Gibraltar and Bab-el-Mandeb.