Qiandao Lake's pleasures divide between the underwater world — diving in the submerged ancient city of Shicheng, the primary reason to make the journey — and the surface attractions of boat trips between forested islands, clear-water swimming, and the melancholy landscape of a drowned valley. The quality of the water is the unifying thread: it is startlingly clear by Chinese standards, and the clarity makes everything, above and below the surface, more rewarding.