Hundreds of thousands of tide viewers have been thrilled by the magnificent Qiantang River tidal bore in east China's Zhejiang Province, as the unique natural phenomenon ushered in its best viewing day on Friday. 

A tidal bore is a phenomenon where the leading edge of an incoming tide creates a wave that surges up a river against the flow. It is caused by the tide-generating force, resulting from the gravitational attraction between the Earth, the moon and the sun. The centrifugal force produced by the Earth's rotation and the trumpet shape of Hangzhou Bay in Zhejiang makes it easy for the tide to come in but difficult to ebb, thus giving rise to a large tidal bore, which is called the "Silver Dragon" by locals.