sea change

a striking change, as in appearance, often for the better.

any major transformation or alteration.

a transformation brought about by the sea.

Origin of sea change

First recorded in 1600–10

Despite the hard work of women like Fonda, Archer said, there had been no sea-change in attitudes within the industry.

Anne Archer: Women in Hollywood Are Doomed Forever |Nico Hines |August 19, 2014 |DAILY BEAST
Some 500 miles off the tip of India, the Maldives have gone through a sea-change since 2008, when Nasheed was sworn in.

In the Maldives, a Coup in Paradise |Sumon K Chakrabarti |February 9, 2012 |DAILY BEAST
All the same, it's suffered a sea-change under your accomplished hands, Langley.

A Young Man's Year |Anthony Hope
But as soon as he had reached the door his manner suffered a sea-change.

Cleg Kelly, Arab of the City |S. R. (Samuel Rutherford) Crockett

Like all the rest of us, he, too, had suffered his sea-change and was the better and bigger man for it.

Pirates' Hope |Francis Lynde
Even the deepening twilight can not disguise the evidences of a terrible “sea-change.”

Sword and Gown |George A. Lawrence
He has suffered a sea-change; for his keel has been wetted in the waters of Eternity.

The Atlantic Monthly, Volume 16, No. 95, September 1865 |Various

sea change

a seemingly magical change, as brought about by the action of the sea

coined by Shakespeare, in Ariel's song ``Full Fathom Five'' in The Tempest (1611)