It is as clear as mud. 
→하나도 모르겠어요.

[예문]

A:That was one long planning meeting.
  기획회의가 너무 길었어.

B:You can day that again.
  And I feel like we accomplished nothing.
 맞아. 그런데도 아무 성과도 없는 것 같아.

A:And what about all that financial jargon.
  I was lost. Was it clear to you?
 재무에 관한 전문용어는 또 어땠는데.
 전혀 이해가 안 되더라. 무슨 말인지 이해했어?

B:yeah… as  clear as mud. 
  이해하긴 하나도  모르겠더라.