The material below is Open Game Content from a 3PP Source
This animate pile of mud seems barely able to maintain the semblance of a humanoid form made of dripping sludge.
Environment any land or water (Plane of Earth)
Organization solitary, pair, or gang (3–8)
Earth Glide (Ex) A burrowing mud elemental can pass through dirt, gravel, or other loose or porous solid matter as easily as a fish swims through water. It cannot use this ability to pass through a solid barrier such as a stone or brick wall. Its burrowing leaves behind no tunnel or hole, nor does it create any ripple or other sign of its presence. A move earth spell cast on an area containing a burrowing mud elemental flings the elemental back 30 feet, stunning the creature for 1 round unless it succeeds on a DC 15 Fortitude save.
Entrap (Ex) The mud from an elemental's entrap ability can be washed away in 1d3 rounds of immersion in water.
Where the Plane of Earth borders the Plane of Water, a mixing of the fundamental elements occurs—it is in this borderland that the mud elementals dwell. Scorned by earth and water elementals, mud elementals usually look like vaguely recognizable blobs of mud in the shape of a Material Plane creature, whether a humanoid, an animal, or even an immense insect. The exact density of their muddy bodies varies—some might be composed of silty water, while others are thick, like river clay. Large and powerful mud elementals tend to have worm-like, reptilian, or frog-like forms.