On the river, the water is like the sea. What is its genre?

The seven-character poem "On the Value of the River as Sea Water" is a seven-character poem written by Du Fu, a great poet in the Tang Dynasty. This poem is a poem that the poet expresses his inner feelings in the face of the turbulent river like the sea. This poem was written during the Anshi Rebellion. The poet lived in Chengdu, Sichuan, and lived in a thatched cottage. Once, when he saw Jinjiang's "water is like the sea", he was deeply moved by that scene, and he felt a lot, but there was no way to talk about it. He had to "briefly talk about it" and express his angry, self-relieved and temporary life feelings. There are eight sentences and fifty-six words in the whole poem. Among them, "Words are not astonishing and endless" is a famous sentence handed down from generation to generation, which shows the characteristics of Du Fu's poems and his serious and rigorous writing attitude.