The story
From sea + change; sense 1 (“movement of people from cities to rural coastal areas; act of relocating from an urban to a rural coastal community”) was possibly coined by the Australian author and demographer Bernard Salt in his book The Big Shift (2001), based on the title of the Australian television series SeaChange (1998–2000 and 2019) about a lawyer who moved with her daughters from the city to a coastal town.
Etymology from Wiktionary, CC BY-SA 4.0.