The possibility of distinguishing between turbulence and wave fluctuations of the hydrodynamic fields is discussed. Possible mechanisms of generation of turbulence in the ocean are considered, and theoretical information as well as experimental data are given concerning the spectra of small-scale turbulence in the upper layer of the ocean. Intermittent turbulence in the main body of the ocean is described. The laws governing the turbulent diffusion in the ocean are briefly considered. A hypothesis is advanced concerning the spectral transport of the mean-squared vorticity in the field of quasitwo-dimensional turbulence. The small-scale convection produced by the difference between the diffusion coefficients of heat and salt in sea water is considered. Experimental data are presented on the vertical thin-layer microstructure of the ocean, and possible mechanisms whereby it is generated are considered, such as shear instability, internal waves, lateral convection, and differences between the diffusion coefficients for momentum, heat, and salt. The distortions produced in the internal-wave spectra by the presence of vertical thin-layer microstructure are analyzed.