深海里的鱼看不到天的透明
[shēn hăi lĭ de yú kàn bù dào tiān de tòu míng]
This implies a sense of loneliness and isolation; like a fish in the deep sea cannot see the sky, this individual might not experience what many would consider normal or clear parts of life due to where 'they swim' - emotionally, socially, etc.