‘Tidal mixing’ describes tidal mixing in shelf seas, where the water is shallow and tidal currents can be much faster than in the deep ocean. Most of the energy lost from the tide through friction is first converted into turbulence, which then makes a very effective mixing mechanism, stirring the Sun’s heat downwards. Shelf seas at temperate latitudes in summer are divided into stratified regions and vertically mixed regions, depending on the tidal streams’ strength and the water depth. The transition from one to the other happens rapidly and creates a tidal mixing front. Tidal mixing in estuaries is also discussed along with the harnessing of tides to generate electricity.