What could cause someone to black out, fully conscious in the shower. lasted for less than a minute. vision came back hazily at first and then fully?

Postural Hypotension: Low blood pressure is a common cause of "blacking out" that can be benign--unless, of course, the person hits his/her head on the way down. There are many other reasons why one would black out: medications, malnutrition, stroke, low blood sugar, dehydration, diabetes, seizure, infection, fever, and more. See your doctor for a complete physical and blood work.