Sea change is a term often used in politics that refers to a surprising and significant change from a previous position.
Early sailors were very familiar with the sudden and unpredictable temperament of the sea, which was calm one minute and life-threatening and dangerous the next.
They introduced the expression “sea change” into everyday English language meaning any sudden transformation.
When someone suffers a “sea change”, it means it was a sudden change.
The phrase came from Shakespeare’s The Tempest.