Fish can't express themselves without water, that is, they can't express themselves without books. The national map is the meaning of the national library. The national map is like the sea, which shows that knowledge is boundless, water eventually flows to the ocean, and so do fish, which also shows the significance of the national map. It is hoped that many "fish" will return to the "sea" through "water" and many "people" will return to "knowledge" through the culture of "books"