The major attraction near Hong Kong for adventurers who yearn for the varied landscapes of nature, Sai Kung Peninsula in the New Territories is an adventure setting in high demand because it has yet to see the rampant urbanization that has swept through Hong Kong and Kowloon. A place for the hiker, swimmer, diver, or contemplative warrior-poet in you, Sai Kung is home a number of varied outdoor attractions.
For the scuba diver and snorkeler, there is Hio Ha Wan, a pristine bay high in coral and diverse marine life, as well as a few wrecks for divers of all ability levels. Tai Long Wan is a remote and picturesque beach along the MacLehose Trail, and is really as pristine and untouched as photos make it out to be (just be careful in the water; the currents can be tough and there are no shark nets).
The best hikes can be found along the aforementioned MacLehose Trail, a 100 km (62 mile) trek through the New Territories that includes 463 meter (1520 foot) Sharp Peak. Then again, you may also choose to walk any number of other trails, including the interconnected beaches of Tai Long Wan on the eastern shore of the peninsula, which can legitimately cover a full day with stops in a few beach-side restaurants to grub down. If you want to make your Hong Kong travels more spectacular than the typical ferry ride in Victoria Harbour, then spend a few days on the Sai Kung Peninsula.
Note:The tiny town of Sai Kung (Clearwater Bay Road to Hiram's Highway if you're driving from Kowloon) will be your best bet for cheap and delicious seafood while in Hong Kong. Twenty minutes away from the highly congested bustle of the city and a number of options overlooking the ocean aren't so shabby an option if you're looking for something good to eat.