When the mistral blows
Stay away from the west side beaches (Kathisma, Porto Katsiki, Egremnoi) because the waters there are very deep and the waves can become dangerous. You can go instead to Agios Nikitas beach and all the east side beaches (Lygia, Nikiana, Nydri, Vassiliki) whose waters are always calm.
No swimming suit
If you are a fan of nudism, then Pefkoulia will become your favorite beach. It can be easily accessed, it is semi-organized and doesn't get as crowded as the other popular beaches during the peak of the summer season. Right after the big rock you will find the nudist area.