This chapter describes the semidiurnal internal wave global field and global estimates of internal tide energy. One of the most important ideas presented here is the strong generation of internal tides over submarine ridges. Energy fluxes from submarine ridges related to tidal internal waves exceed many times the fluxes from continental slopes. Submarine ridges form an obstacle to the propagation of tidal currents that provides internal tide generation because tidal currents obtain a vertical component over the ridge slopes. Energy fluxes from submarine ridges account for approximately one fourth of the total energy dissipation of the barotropic tides. Combined model simulations and moored measurements result in a map of the global distribution of internal tide amplitudes.