Lido di Lugano is the city's easiest summer answer to the lake. It combines swimming pools, lawns, beach access, and broad views across the water, so you can choose between a proper pool swim and a lazier afternoon by Lake Lugano.
It is popular with locals as well as visitors, which keeps it from feeling like a resort bubble. In hot weather, come early or accept the crowd; the payoff is a swim with mountains in the background and the city only a short walk away.