Monsoon season

This phenomenon is something that occurs every year when the monsoon rains cause loads of sand and dirt to be flooded into the Yangtse or Yellow river. This is actually the reason why the nickname of the Yangtse River is "Yellow River". This dirt and sand colour the water yellow.
Now in Bohai Bay this water meets the ocean water. The colour difference is beautiful and a very strange but perfectly explainable phenomenon.

Fresh versus salt water

Because of the difference in density between fresh water and salt water, the mixing happens very slowly. So slow, you actually can't see it happen. Therefor it's like there is a wall between the two "kinds" of water. Amazing sight and a freak of nature, but a beautiful freak!

Sincerely,

Pele23