“Sekine-san said he is sorry that he left this company, but that he considers it water under the bridge.
In hot water
To be in big trouble
“Endo-san is in hot water with her boss because she refused to work overtime last weekend.”
Like water off a duck’s back
To ignore criticism
“A politician has to learn to let criticism roll off her like water off a duck’s back.”
Test the waters
To try something on a limited basis as a test
“The company is going to test the waters in the cosmetics market with a new skin cream.” Note on the origin of this phrase: One dips a toe in the water to see if it is too cold to swim.
Throw cold water on something
To attempt to find fault with something to slow or stop it
“Management might be throwing cold water on the research project because it is becoming too expensive.”