海不会不蓝可你却会不在
[hăi bù huì bù lán kĕ nĭ què huì bù zài]
'Hǎi bù huì bù lán kě nǐ què huì bù zài' meaning 'The sea cannot help but stay blue, however you can choose not to be with me.' It portrays a sentiment regarding parting. Although the ocean keeps being blue eternally, you may eventually choose to leave, implying changeability of personal relationship compared with the unchangeableness of nature. This is typically used for feeling sad about leaving behind.