Pour/throw cold water on something British American informal verb phrase
To spoil someone's ideas, plans or enthusiasm by criticizing them
He is always pouring cold water on my opinions.
Although my colleagues in the office thought my idea was great, my boss threw cold water on it.
She poured cold water on the whole project by refusing to participate.
To destroy or put a damper on one's hopes or dreams
To really upset, annoy or disappoint someone
To make someone really upset, irritated or disappointed
The verb "pour/throw" should be conjugated according to its tense.
This is one of those phrases that started out as literal and then as per usage became figurative.
To be very wet
Because of forgetting bringing an umbrella, I look like a drowned rat when it rains.