Adults typically learn fast because they are eager to learn! Of course, it always depends on how in shape you are and whether you are already active. If you are already active, then after 8 days, you can expect to have gained stroke development skills in both freestyle and backstroke, including proper breathing for freestyle, proper kicking and arm stroke, back floating, deep water exploration that includes treading water, jumps, dives and reaching for rings. I have seen some adults water safe after 8 days. Of course, I recommend continuing to practice for best results.