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From 张志和's 《和渔夫词》 (Tang): 鱼龙混杂一川中 - fish and dragons stirred together in one river. Originally a neutral image; later specialized into 'good and bad mixed', usually with a negative tilt.
usage
Slightly negative - the situation is problematic because the 'fish' (ordinary/honest) and 'dragons' (trickster/powerful) are indistinguishable. Ironically, the implied 'dragon' reading here is 'bad': in 鱼龙 context the dragons are the troublemakers.
