Most are pretty inaccessible. Lia beach seems to be fairly typical. It is a 30 min walk downhill and is an attractive pebbly beach with some shade. Few others cared to make the journey and those that did didn't bother with swimsuits. Grammata, Varvoussa and some others are less secluded because they are more popular with boats of various types.
None are really practical as regular holiday beaches unless one has use of a boat.
If walking to see the old ruins at Kastri, a swim at Klysoura is recommended as a short detour.