I've lost more horses and other beasts of burden to swamps than all the monsters I've fought combined. It's ludicrous. When faced with a swamp of the vine dripping horror type like you see in the motivator today I prefer to leave my mount behind. I mean seriously, when you fight monsters they tend to at least leave your horse wounded so you can heal it back up again. Not swamps. They swallow those suckers whole. No save or anything. Insta mount death. No I've not been in lots of games where my horse was absorbed by a swamp, why do you ask? This is why when I'm an arcane spell caster I prefer to ride in style on an arcane disk. That however is a completely different post for a completely different time.
I had the author's name for the art but they're gone from the internet now