Naked girls doing naughty things at this party

Casey has figured out he can use his little sister Stacy/Vina through her gym. Stacy knows how to make people harder to work with and he really just wants to get them to take a naughty selfie. They keep doing this, until the girls are slobbing around him and naked in the gym. The girls find Stacy distracting and start to get in to the action, so they do another crazy pool party.