This is what youre looking for in a marshy/swampyarea

a. A pool of water or mud where animals go to wallow.

[/align]b. The depression, pool, or pit produced by wallowing animals.

We found some the other day on public land not too far from the farm and I tell you there had to have been 70 deer using that wallow. Not to mention you can smell the estrus and musk before you even find one.