There are few beaches on Hong Kong Island you can reach after a hike, rewarding your efforts with relaxing scenery, a cool swim and perhaps even some rolling surf. I'm going to suggest a fantastic and scenic route.
Starting from a bus stop at the beginning of Shek 0 Road is a great trail that leads up and over Dragon's Back, perhaps the finest short hike in Hong Kong If you have time to spare, first head down from the bus stop to the beach at To Tei Wan which, though not a fine swimming or sunbathing beach, has a quaint abandoned village and is home to the Hong Kong Hobie Club. You'll see the members' sailboats arrayed along the sand. From there, start climbing backs the Hong Kong Trail, which leads through trees and bamboo and up a scrubby hillside. Turn right at the top of a steep flight of steps, and you'll come to a cluster of boulders, with great views across Tai Tam Bay to Stanley.
Retracing your steps from the boulders, continue along the meandering path, then take a right turn, uphill again. In minutes, you'll be on the Dragon's Back ridge, savouring brilliant views down to Shek 0 and across the sea to Tung Lung Island and the Clearwater Bay Peninsula.
When the northeast monsoon is blowing, Dragon's Back is popular with paraglider pilots who climb up with their heavy packs, then launch themselves from grassy slopes, hang in the air, and eventually drift down to a beach at Shek O.
The trail heads north now, sometimes burrowing between bamboo and shrubs then climbing to a hilltop with more outstanding views. Big Wave Bay soon appears below you - a short stretch of sand in a narrow cove between rocky headlands. Then, the Hong Kong Trail drops, turns away from the ridge, and you've seen the last of Big Wave Bay for some time. Follow an easygoing woodland trail, crossing occasional small streams. The trail emerges close by a correctional services centre near Tat Tani Gap. The beach is closer now; just follow the signs pointing along a service road, then take a right, to drop down, and at last arrive at Big Wave Bay.
Big Wave Bay seems far removed from most of Hong Kong Island: walking to it, you pass through a small village, with houses amidst fields, the hillside stretching above. Though it's small, there's a good beach, with a lifeguard service in summer, and facilities including showers. It's a fine place for unwinding and swimming after a hike. Big Wave Bay is a magnet for surfer dudes, who have only ripples to ride in calm weather, but arc drawn here when a typhoon roars close by and surf's UP! You'll be happy to stroll along the rocky shore to the left and path leads to an old rock carving - perhaps a bit boring to look at, though the location is good, with more views of this marvellous stretch of coastline.