萍水相逢　

◎ 萍水相逢 píngshuǐ-xiāngféng

(1) [(of strangers) meet by chance like patches of drifting duckweed] 比喻素不相识之人偶然相遇

俺与你萍水相逢,出身相救,实出恻隐之心。——清· 冯梦龙《警世通言》

(2) 亦作“萍水相遇”