深海不知天蓝孤鸟不懂群暖
[shēn hăi bù zhī tiān lán gū niăo bù dŏng qún nuăn]
Deep sea does not know the sky is blue, solitary birds don't understand flock warmth. A person might use this as their internet nickname if he or she is introverted or isolated, like someone in a lonely environment who is unfamiliar with the warmth of crowds and companionship, similar to the situation where deep seas don't experience the blue skies and solo birds haven't known flock support.