April-May and July-August every year. "Blue Tears" is a kind of glowing seaweed. The hotter the weather, the more vigorous this algae is, and the more obvious the blue light is. Red light, orange light and yellow light with long light waves are absorbed by seawater because of their slow propagation speed, while blue light and purple light have short waves, fast propagation speed and slow absorption, which can be observed by human eyes. Therefore, blue tears appear frequently in fishing ports in April-May and July-August every year.