"No Sh*t Sherlock?"?

Question

What does "no **** Sherlock" mean?

Answer 1

duh!

Answer 2

"Thank you captin obvious"

It is a scarcastic statement telling you that you are stating the obvious and that you have told that person something they already know.

Answer 3

Sherlock Holmes was a very famous fictitious detective.  The character was a genius who could take the tiniest clues and solve a crime.

But what would you say if he pointed out something that was obvious even to you?

Duh.  That's obvious.  You might even roll your eyes.

That's what the phrase is.  You're sarcastically making fun of a person who's pointed out something to you that you already know.