expression, godan verb (-su)
pour water into; dilute with water
Literal meaning: to add water to something, often to dilute or adjust consistency. Used for drinks, soups, paints, etc.
スープが濃すぎたので、水を差して薄めた。
The soup was too thick, so I added water to thin it.
絵の具に水を差して、色を薄
I add water to the paint to lighten the color.
expression, godan verb (-su)
throw cold water on; put a damper on; hinder
Idiomatic use: to spoil a good atmosphere, interrupt a smooth conversation, or discourage someone's enthusiasm. Often used when someone says or does something that ruins the mood.
彼の一言が楽しい雰囲気に水を差した。
His one remark threw cold water on the cheerful atmosphere.
せっかく盛り上がっているのに、水を差すようなことを言わないで。
We're finally getting excited, so don't say something that will put a damper on it.