A phrase often used towards someone who states the obvious.

It’s an acronym standing for Can’t Remember A Fucking Thing. It’s usually used to describe embarrassment at being unable to remember someone (CRAFT moment); going onstage as the lead in the latest theatrical performance and your mind goes completely blank (CRAFT situation); the next morning after a night when you got pissed as a fart and woke up in bed cuddling a traffic cone and a string of fairy lights wound round your prick.

When someone says something that is very obvious

meaning 'well of course dumbass!'
other phrases like this include grass is green

It's like the person said something that was pointing out the obvious....kinda like "no duhh!"

duh.

what you say when someone says something very obvious.

Stating something obvious, this is a sarcastic way of saying "It's very obvious, you can shut up now."

The victim can follow up with "Fuck you Watson" or similar to defend themselves.