Tai Tan country trail is a beautiful and easy country trail at the very far end of Sai Kung. It offers some nice views to archipelago and mountains of Sai Kung. But if you plan on doing it on a sunny and hot day, you should be aware that the trail is mostly sunny making even the moderate climbing much tougher.
Beyond easiness and views, another reason for doing the trail is that it ends at Hoi Ha, which is a tiny village offering the possibility to not only rent canoes but also to snorkel. What surprised me is that you can even see corals there, but be aware of the jelly fish which were relatively wide spread atleast when I was there. I have read that on sundays it is recommended to book a canoe in advance but base don my own experience it is not really needed. There are many operators on the beach, but I have also used the one which you reach after going through the village (the one on the right side if you look from the sea).
Hoi Ha has also a beautiful beach which is relatively small on high tide but quite big on low tide.
To get back to Sai Kung town you have to take a minibus which goes every 30minutes and often has a long line meaning you often cannot fit in the first one.