A mudﬂat along a coastline is a level area of ﬁne silt continually exposed by low tide, never quite drying out before high tide returns; it’s usually associated with or sheltered by coastal estuaries, sand spits, shingle bars, barrier islands, or cheniers. In a lake, river, or wetland, however, a mud-ﬂat, while also associated with such sheltering formations as islands or wide, lazy bends in a river, gets its water not so much from tides but from extremely gradual contours of the land. Such contours allow the lake or river to periodically wash up and cover the mudﬂat in shallow water, which drains slowly, both downslope to the river or lake and straight down to a shallow water table. In either case—ﬂuvial or marine—a mudﬂat is characterized simply by a big, ﬂat, often bad-smelling expanse of mud, one that, because it strands insects and small animals, tends to draw birds (though in the case of Olympia, Washington, the local mudﬂat draws Evergreen College’s graduating seniors for a nude race). The main difference in ﬂuvial and marine mudﬂats, aside from sources of water, is that while a ﬂuvial mudﬂat has dry periods, in which the mud on the surface acquires a salty crust and cracks, a marine mudﬂat stays wet year-round, sometimes even—as happens in Alaska— trapping the occasional person in a suction grip while water steadily rises. The trick in that circumstance is to run a stick or handle down your leg and move it sharply to the side, allowing enough air in to break the suction. And then take your stick with you, for the next step.