Before revision: thumbnail|300px|Effect of a pressure surge on a float gauge Hydraulic shock (colloquial: water hammer; fluid hammer) is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly ; a momentum change.
After revision: thumbnail|300px|Effect of a pressure surge on a float gauge Hydraulic shock (colloquial: water hammer: fluid hammer) is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly ; a momentum change.