There are two Amopi beaches: Mikri (Little) and Megali (Big). Mikri Amopi is small and quiet, with mostly serious sunbathers. Megali Amopi is the most popular. There you will find a mix of older and younger tourists, Greek-Americans, and locals. There are 3 restaurants at Megali Amopi and a Bar/Cafe called "Avra" where the young people drink coffee and play tavli (backgammon) and/or play beach volleyball next to the cafe.
On the other side of Megali Amopi there is a beach called "Kastelia". It is primarily for nudists, even though nude beaches are against the law in Greece.