Le Sirene Beach
This small beach is located behind the port of Amalfi, named for the restaurant and bathing establishment that runs it, the Lido delle Sirene. It's a rather small section of seafront, wedged between a breakwater and some rock outcroppings, but since it's outside the port area, the water is generally clean. It's a nice choice because it's in town and so easily accessible by public transit as well as by car (and with parking available in town), and all the services and refreshments you'd want are close at hand.
It faces south and gets the sun throughout the afternoon.
Rent a holiday house in Amalfi and travel like a local.