Agropoli has good beaches for a town of its size, and the water quality in this part of the Cilento coast consistently earns Blue Flag certification. The main town beach, Lido Azzurro, stretches north of the marina and has both free sections and paying lidos with sunbeds. It gets crowded in July and August.
For more space, the beaches south of the promontory are better. Baia di Trentova, a small cove about 2km south of the centre, is sheltered and has cleaner water than the town beach. You can reach it on foot from the old town along the coastal path, though the last stretch is steep. The coves further south along the Cilento coast — accessible by car or boat — are significantly less crowded and scenically finer.
The sea here is warm enough for swimming from June through October. Note that the paid lidos control access to the best sections of sand; the free beaches can be rocky in places but are fine with water shoes.