Definition from Wiktionary, the free dictionary
Alternative forms 
- (idiomatic) A profound transformation.
- Public opinion has undergone a sea change since the 2002 elections.
- c.1610-1611, William Shakespeare, The Tempest, Act 1, Scene 2,
- Full fathom five thy father lies: / Of his bones are coral made: / Those are pearls that were his eyes: / Nothing of him that doth fade / But doth suffer a sea-change / Into something rich and strange.
- 1910, Jack London, Theft: A Play In Four Acts, Actors' Description of Characters,
- Anthony Starkweather. […] Essentially a moral man, his rigid New England morality has suffered a sea change and developed into the morality of the master-man of affairs, equally rigid, equally uncompromising, but essentially Jesuitical in that he believes in doing wrong that right may come of it.