as clear as mud不要直接理解为“像泥土一样清楚”，应该理解为“像泥土一样不清楚、乱糟糟的”，也就是“极难理解、难懂”之意。

【例句】
I guess I need to call a lawyer because these legal contracts are as clear as mud.
我想我需要请个律师，因为那些法律合同极难理解。

Your report was badly written, it was as clear as mud.
你的报告写得很糟，简直看不懂。