Her slutty nature makes her boyfriend decide to break up with her.
Cantonese
不谙水性
不諳水性
not good at swimming
Examples (Wiktionary)
Mandarin
水性
水性
shuǐ xìng
swimming ability
Mandarin
不习水性
不習水性
bù xí shuǐ xìng
to not know how to swim
Mandarin
通过几天的相识，我了解到你是郑州女孩儿。当然，你的北方口音和河南方言可是经常闹出不少笑话。我好不容易适应你口中的“水笔”（水性笔）啊“卫生纸”（口纸）啊，新的笑话又来了——
通過幾天的相識，我瞭解到你是鄭州女孩兒。當然，你的北方口音和河南方言可是經常鬧出不少笑話。我好不容易適應你口中的“水筆”（水性筆）啊“衞生紙”（口紙）啊，新的笑話又來了——
tōng guò jǐ tiān de xiāng shí ， wǒ le jiě dào nǐ shì zhèng zhōu nǚ hái r5 ． dāng rán ， nǐ de běi fāng kǒu yīn hé hé nán fāng yán kě shì jīng cháng nào chū bù shào xiào huà ． wǒ hǎo bù róng yì shì yìng nǐ kǒu zhōng de “ shuǐ bǐ ” （ shuǐ xìng bǐ ） a “ wèi shēng zhǐ ” （ kǒu zhǐ ） a ， xīn de xiào huà yòu lái le —
After a few days of meeting, I learnt that you were a girl from Zhengzhou. Of course, your northern accent and Henan dialect were a fountain of jokes. I put a lot of effort to get used to your "water pen" (gel pen) and "sanitary paper" (facial tissue) and so on, and new jokes just keep coming forth