In the small house settlement of Psathi on the Eastern side of Ios you will find a large beach. The spot you reach the beach from the road has large rocks but if you go further down on your left you will find a sandy patch with umbrellas and sunbeds and even further on the left the best spot of the beach, a more isolated patch. At Psathi Beach one can relax and enjoy its clear blue water.
Very close to the beach there is a taverna, bit higher from the beach. On the road leading to Psathi I strongly recommend you visit the ruins of the Old Castle 'Paleokastro'. The snake shaped pathway heading to the ruins can be a bit overwhelming under the sun but I promise a jump on the sea right after will cool you down perfectly.