Agios Prokopios is the closest good beach to Hora, a 10-minute drive south of town, and it earns its popularity. The sand is fine and pale gold, the water is shallow and clear for a long way out, and the combination makes it the best family beach on the island. Sunbeds and umbrellas are available for hire across most of the bay, tavernas sit at the back of the beach, and the whole setup is efficiently organised without being unpleasantly crowded — at least outside August, when everywhere on the island fills.
The beach curves in a gentle arc between two low headlands and is sheltered enough to stay swimmable when the meltemi kicks up elsewhere. The north end of the bay, closest to the dunes that mark the border with Agia Anna, is quieter and less developed. The water is the standard Cycladic blue that photographs never quite capture; it goes from pale turquoise in the shallows to deep cobalt surprisingly quickly, which means good snorkelling over the rocky patches at the edges of the bay.
If you're based in Hora without transport, the bus to Agios Prokopios runs frequently in summer and drops you near the beach entrance. With a car or scooter, the parking at the north end of the bay is easier and keeps you closer to the quieter section of beach. The beach strip has no shortage of places for a long lunch.