Der Mensch besteht zu 80 % aus Wasser, so ist es nur verständlich, dass water idioms in der englischen Umgangssprache regelmäßig vorkommen:

like a duck takes to water = wie von selbst

z.B.:

This woman learned salsa dancing like a duck takes to water.

could talk under water = redet sehr viel

z.B.:

This guy never really shuts his trap, he could really talk under water.

water under the bridge = das interssiert niemanden mehr

z.B.:

Don´t dish up that old story, that´s water under the bridge.

come hell or high water = komme was wolle

z.B.:

I will go to Australia this year, come hell or high water.