Shanna gets wet and messy

Shanna the She-Devil and Wolverine make their way through the treacherous Savage Land; enduring the elements, muddy terrain, as well as the native predators...

However, after being caught in the middle of a conflict Shanna is left mortally wounded with her only chance being that of an ancient ritual...   

Taken from Marvel Comic's Savage Wolverine #2 and #4 (2013)

Kriss of Valnor falls face first into muck

Wading through the swamp, Kriss of Valnor, too busy admiring herself in her mirror, trips and falls face first into the muck. Demanding help from the gleefully onlooking Aaricia, the two end up scuffling in the mire. Taken from the English translation of the Belgian comic book Thorgal #5 (2009)  

White Rabbit (and Arcade) fall into mud pit

White Rabbit (and Arcade unfortunately) fall into a mud pit. To add insult to injury, White Rabbit also gets egg in her face, literally. From Marvel Comic's Wolverine & Black Cat - Claws II #3 (2011) 

Wonder Woman face down in the mud

Wonder Woman gets beaten and left face down in the mud by the god Apollo. From DC Comic's Wonder Woman #11 (2012)

Credit also to UMD's Nation_of_isWAM for this spot

Titania gets covered in muck

Nemesis of She-Hulk and supervillainess Titania gets punched by her rival, and sent flying...

Later on we find out that, unluckily for Titania, she had landed straight into a pile of muck.

Taken from Marvel Comic's She-Hulk #09 and #10 (2005) 

Durham Red falls into mud

Durham Red of the Strontium Dogs flees an ambush- right off the top of a ravine and into a mud flat. From 2000 AD Prog #1785 (2012)

Credit to MrZero for this find

Talia splattered with clay

Talia Al Ghul gets splattered with clay in her encounter with Clayface from DC Comic's Young Justice #12 (2012)

Credit to Mr. Zero for this find

Ms. Marvel falls into river of slime

Ms. Marvel falls into a river of slime and gets covered in gunk from Marvel Comic's Ms. Marvel #21 (2008)

Betty and Veronica in another bog

Betty Cooper and Veronica Lodge slip into a bog from Archie Comic's Archie 1 The Dawn of Time (2010)

Credit to MrZero for this Archie Comics find!

Betty and Veronica fall into bog

Betty Cooper and Veronica Lodge fall into a bog, getting covered from head to toe in mud! Taken from Archie Comic's Betty and Veronica Digest #57 (1980)

Credit to MrZero for this Archie Comics find!

Wonder Woman covered (cont.)

Wonder Woman covered head to toe in muck facing off against Clayface from DC Comic’s Wonder Woman #160 (2000)

(also see http://comic-book-wam.blogspot.co.uk/2011/10/wonder-woman-covered-from-head-to-toe.html for the cover of this issue)

Batgirl covered in muck

Batgirl gets covered in gross muck in DC Comic’s Batgirl #13 (2010) alongside original artwork by Stanley "Artgerm" Lau

Black Canary and Crimson Fox wrestle in muck

The Elongated Man watches on as Black Canary and Crimson Fox get muddy from DC Comic’s Adventures of Superman Annual 4 (1992)

Wonder Woman covered from head to toe

Wonder Woman covered from head to toe in clay from DC Comic’s Wonder Woman #160 (2000)