Zhihai is not a sea, but a grassland. Only one kind of grass grows in it, Zhihai.
The mandarin orange grows wither every day, reaching half a foot high at noon, and only withered roots remain at midnight.
On this planet, 90% of the land only grows this kind of orange grass. Except for Zishi, the rest of the land is surrounded by green orange grass all year round, just like the sea surrounding the land, hence the name Zhihai.
However, the Zhihai Sea has not existed since ancient times. At least three thousand years ago, there was not a single Zhihai grass on the entire land, until...