(prostitutes) to get married; or women living on boats to get married to someone and live on dry land; to get married to someone of a higher social class and live comfortably [colloquial]
Definitions (粵典–words.hk)
語句、黃賭毒
指妓女從良，唔再賣身；本意應該係指水上人上岸上生活，後來變成唔再做一啲嘢嘅意思 to stop working as a prostitute, to retire from prostitution; literally: to go to the roadside and drink well water