Mesotidal deposits are formed where the tidal range is between 2 and 4 m, but, as with the macrotidal deposits, the limits are not sharply defined. They may vary because of diurnal or longer-term inequalities in the tidal range, short-term variations related to the wind regime, and variations in tidal range within the same intertidal area. Nevertheless, mesotidal deposits, grouped within the loose limits used here, have some common characteristics and are usually associated with sandy barriers, barrier islands, spits, tidal deltas, and inlets (Hayes 1975). Like macrotidal deposits, mesotidal deposits are only found where there is shallow coastal water, an open coast or an open connection with the sea so that the tides can come in, and granular material available for building up sediment. In some large, mainly mesotidal areas, such as the Wadden Sea and the north coast of South America between the Amazon mouth and the Orinoco delta, the tidal range varies from microtidal to macrotidal, but the mesotidal deposits dominate, so they are grouped in this chapter.