The issue opens with a discussion of the problems associated with the description of the complicated motions of liquid media, which are accompanied by a multi-scale complex of non-equilibrium processes, including relaxation and inertial effects. The results of high-resolving modeling for the surface semidiurnal tide M2 in the Laptev Sea are discussed. They are obtained using a high-resolving version of 3D finite-element hydrostatic model QUODDY-4. The development of a software package IGWResearch2 is considered. This package contains numerical models, hydrological data, data preparation tools, analysis tools and observations’ information related to internal waves in the World Ocean. The results of the light attenuation coefficient measurements in the range of 400—800 nm in the waters of Lake Teletskoye obtained in a summer cruise (19—23 June 2018) are presented. The results of interferometric processing of the oceanographic large-scale experiment SWARM-95 on the coast of New Jersey are discussed. The results of calculation of the hydrodynamic interaction of the impeller, guide vanes and the pump-jet guide nozzle, obtained on the basis of numerical methods of viscous fluid dynamics, are presented. The paper describes a method for passively determining the distance to an underwater source using the curvature of the wave front of the source field in the Fresnel zone. A new (probabilistic) approach to the information processing algorithm of the magnetometer signal is proposed, which determines the width of the recommended search band of an object with guaranteed values of the probability characteristics of its detection. The bibliographic paper about one of the founders of inland hydrology Mikhail Andreyevich Velikanov is presented.