桃花潭水深千尺，不及汪伦送我情。
The Peach Blossom Pool is a thousand feet deep, but not as deep as Wang Lun's friendship for me.
—— 李白
Source: 赠汪伦(To Wang Lun)
Background
From Li Bai's "To Wang Lun," a famous verse expressing deep friendship through the ages.
Interpretation
The water of Peach Blossom Pool is a thousand feet deep, but it cannot compare to Wang Lun's deep affection in seeing me off. This uses exaggeration to express the sincere and deep friendship between friends.