别以为你姓余就会游泳
[bié yĭ wéi nĭ xìng yú jiù huì yóu yŏng]
A playful name suggesting a misunderstanding; just because your surname is 'Yu' (meaning 'fish' or associated with water in Chinese) doesn't mean you know how to swim. It’s humorous while hinting at the fallacy of assumptions.