This is my favourite place in Hong Kong, perhaps even in the world. This beach is part of the MacLehose Trail that winds in and out of the coast of the New Territories for about 100 kilometres. You can catch a bus from Sai Kung town to Pak Tam Au and join the trail from here. It's not an easy walk and it will get your heart racing, but the views are incredible.
I remember the second time I went to this beach I actually ran the last kilometre—I was that excited. As you make your way through the few houses and shacks you'll burst upon paradise, cross over the little, rickety bridge, through off your shoes and the beach is yours.
You can camp here over night. (The basic restaurant has tents, sleeping bags, and everything you need.) It's beautiful, it's magical, it takes effort to get there, but then again don't all the best places?