Water soaked soil. Mire. Slime. Muck. Goo. Adobe.
Some people still say the Eskimos have 52 words for snow. Be that as it may, I'm pretty sure that from autumn through spring, trail runners have about 52 words for mud. If you include compound words. And phrases.
A lot of them take the form of "(expletive-adjective) (expletive-participle) (redacted) mud!"
Sludge. Ooze. Bog. Slush...