萍水相逢的英文：
[Literal Meaning]
drifting duckweed/water/each other/meet
(of strangers) to meet by chance like patches of drifting duckweed

[解释]
浮萍随水漂泊，聚散无定。比喻人的偶然相遇。

[Explanation]
(of strangers) to meet by chance

[例子]
他们萍水相逢，本来以为再也不会见面了，但是十年后竟然结成了夫妇。

[Example]
They met each other by chance and had never thought they would meet again. But they became a couple ten years later.

[英文等价词]
casual encounter

Improbable friends pledged to be blood brothers.
萍水相逢的朋友歃血结成生死与共的兄弟。

Mr. Luker is only a chance acquaintance of yours
鲁克先生跟你只是萍水相逢罢了。