Anything soggy, soft, and a little muddy is miry. Your bright white sneakers won't look brand new anymore after you hike along the miry riverbank in them.
The adjective miry, which is good for describing places that are boggy or mucky, comes from mire, "a stretch of swampy ground." Mire derives from the Old Norse word myrr, "bog or swamp," and shares a root (meaning "damp") with the word moss. Miry things are damp and squishy, like the ground around a marsh or the muddy surface of a dirt road after heavy rain.