八百里海深七厘米蔚蓝
[bā băi lĭ hăi shēn qī lí mĭ yù lán]
The user is referring to the vast depth of the ocean being a deep, mysterious blue, which might symbolize someone's unfathomable or deep emotions. Here it may imply emotional depths that are complex or not easily understood, comparing one's heart to the fathomless sea.