welcome to this forum and thank you for the compliments!
don't worry for the beach in Polychrono
. It's sandy with a few areas of stones. The beach is narrow on some places, but long. Bathing will be perfect
!! Of course there are many other places in Halkidiki
with beautiful beaches that I can recommend, but Polychrono is one of them!
I always advise everybody to rent a car (at least for 1 day) to see other places and beaches. Have a nice time!