[SunkenCiv]

Changsha bowls from the Belitung shipwreck.

ArtScience Museum, Singapore | Wikimedia Commons

[blueunicorn6]

China’s medieval ties were always too wide or too thin.

[Nateman]

The Antkythera Mechanism, the World's first known Celestial Calculator, was found underwater in 1901 .It is believed to have been designed by Archimedes himself.

[Ruy Dias de Bivar]

I read years ago that, in that time period, the Chinese had explored as far west as East Africa and possibly the West coast of the Americas.

Then their exploration ceased.