沧海有时尽深海夜未眠
[cāng hăi yŏu shí jĭn shēn hăi yè wèi mián]
The Vast Sea Has Its Bounds But the Depths Lie Awake at Night: A poetic reference implying the speaker experiences feelings or thoughts that are profound or endless, but despite this vastness, there is an aspect—perhaps loneliness—that keeps one awake.