This movie was as dull as dishwater, with no plot twists at all.

dishwater 是由 dish（盘子、餐具）和 water（水）组成的复合词，字面意思是"洗碗水"。 在英语中，as dull as dishwater 是一个固定比喻表达，用洗碗水的平淡无味来比喻事物极其无聊乏味。