be (all) water under the bridge
A past occurrence, especially something unfortunate, that cannot be undone or rectified

[TahlilGaran] Dictionary of Contemporary English ▲

water under the bridge
something that has happened and cannot be changed.
I should probably have asked for more money when I was offered the job, but hey, that's water under the bridge now.

[TahlilGaran] English Idioms Dictionary ▲

water under the bridge
something that happened in the past and can't be changed
It was terrible that your house was robbed but it is water under the bridge now and you must move forward.

[TahlilGaran] English Idioms Dictionary ▲

water under the bridge
{n. phr.} Something that happened in the past and cannot be changed.
Since the sweater is too small already, don't worry about its shrinking; that's water over the dam.
Compare: CRY OVER SPILLED MILK.
See: WATER OVER THE DAM.

[TahlilGaran] English Idioms Dictionary ▲