mud_flat has definitions from the field of geography
1
[ noun ] (geography) a tract of low muddy land near an estuary; covered at high tide and exposed at low tide

Used in print

(Stephen Longstreet, Eagles Where I Walk....)

Below in the open bay facing Manhattan was Staten_Island , gritty with clam_shells and mud_flats behind which nested farms , cattle barns , and berry thickets .

Related terms

tract

*