The issue contains the discussions of modeling of the ocean dynamics and marine ecosystems, the results of natural oceanologic experiments as well as applied problems of hydrophysics. Based on 3D-numerical modeling the interaction of the surface semidiurnal tides in the Barents and Kara Seas is studied. The estimates of CO2 flux between the atmosphere and the sea obtained by the ecosystem model of the Barents Sea are given. The coefficients of horizontal turbulent viscosity are calculated on the basis of an increased flow velocity measurement data performed in the heavy areas of the White Sea. The dependence of internal wave images structure on the character the attenuation coefficient stratification is analyzed. The review of practical applications of hydroacoustics which are based on use of the algorithms coordinated with the environment of their distribution is given. The algorithm for solving inverse problems of restoring the vertical sound speed distribution from ship probing acoustic sound diffusers in natural water environment is considered. The division of the World Ocean into parts depending on specifics of zones of spreading to increase the saturation of the Earth’s magnetic field by navigational landmarks is discussed.