Prainha is the most accessible beach from the Platô, about 2 kilometres to the south by taxi or a long walk downhill. It is a small black-sand cove sheltered by headlands, with calmer water than the more exposed beaches on the island's Atlantic coast. The sand is volcanic and dark, which takes some adjustment if you are expecting tropical white, but the swimming is good and there are a few simple cafes and bars at the beach.
For better beaches with more space, head further south toward Quebra Canela or take a taxi to the beaches at Cidade Velha. The beach scene in Praia is low-key and local — you will not find resort infrastructure here, which suits the city's character.