fish in troubled waters 浑水摸鱼；趁火打劫

【例句】
During the economic turmoil, many people fished in troubled waters and made big money.
在经济动乱期间，许多人浑水摸鱼，赚了不少钱。

You delight to fish in troubled waters.
你喜欢趁机混水摸鱼。