clear as mud
Murky, obscure, totally unclear, as in The translation of these directions is clear as mud. This ironic phrase always indicates that something is far from clear. [Early 1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
Examples from the Web for clear as mud
"I thought so, Doctor," says Mrs. Helpalong, and this clear-as-mud evidence against my comfort is reiterated to my mother.