Sai Kung peninsula and Clearwater Bay are out in the New Territories- the area where one third of Hong Kong residents live. The New Territories are hugely popular with locals who want to get away from the city at the weekends and the area around Sai Kung.Penisula is a nice choice.
The area around Sai Kung Town (once a tiny fishing village) is a great place to go for walking, enjoy gorgeous scenery and swim at the great beaches nearby. (Watch out for sharks however!) To see some of the scenery and the beaches, you can hire a small boat to all the islands or one of the nearby beaches (different charges). The boats regularly visit Sharp Island (Kiu Tsui Chau), White Sands Island (Pak Sha Chau), Pillow Island (Cham Tau Chau) and Salt Field Island (Yim Tin Tsai) where there is a small Christian Church.
After a hard day hiking or sunbath on the beach, you can eat in some great little restaurants, such as Pepperoni's Pizza and Cafe on Po Tung Road and the Tung Kee Restaurant which serve exquisite Cantonese seafood on Man Nin Street.