八千米深海七厘米蔚蓝
[bā qiān mĭ shēn hăi qī lí mĭ yù lán]
Translating to 'Eight thousand meters deep sea, seven centimeters of blue', this is metaphorical. It could suggest that the ocean is so vast and deep but only has a very thin surface layer that we see. It may convey feelings of mystery and unexplored depth.