Palombaggia is the beach that put Porto-Vecchio on many Corsica itineraries: pale sand, umbrella pines, red rocks, and water that shifts from clear green to blue. It is beautiful enough to deserve its reputation and crowded enough to punish late arrivals in July and August.
Go early, or come outside peak season when the beach has room to breathe. If you only have one beach day near Porto-Vecchio, this is usually the one to choose.