I've been looking at river banks and large muddy puddles leftover from rain storms. Not a lot around Lincolnshire unless i want to go out into The Wash but there's too much quicksand and mud that it might just be the end of me if i try it.
Is there no kind of mud or clay that i could buy from a shop and fill a paddling pool as that seems to be much safer. The river banks around here just aren't "clean" enough (as clean as mud can get)

What i mean is there's too much crap in it like stones, weeds, bird poop, etc.