Acronym meaning the state of mind that goes along with wearing shorts and flip flops (i.e. acronym is for Shorts And Flip Flops). It's a state of happiness, of being free, a relaxed state of mind. One in which you walk slowly because you're in no rush to get anywhere, and the air around you is comfortable. It is completely understandable for one's goal in life to be saffing for as high a percentage of time as possible.
"So what are you up to?"
"Just saffing down on the boardwalk, checking out the waves. Man I love summer."