Completed Island

Easy Used by Smart Hint

Once an island's marked cells already equal its clue, every cell around it is sea.

Island (land)
Sea
Cells that establish the pattern
Where the conclusion lands

How it works

This island's clue is 2, and it already has 2 marked cells — it's finished, nothing more to add.
Every cell touching the finished island must be sea, or it would merge into it — mark all of them.