GridWits
Medium tier Technique 9 of 18 Used by Smart Hint

Landlocked Cell

A cell fully surrounded by land can't be a lone patch of sea with nowhere to connect — it's land.

How it works

  1. 1The top-right corner has only two neighbors, and both of them — the 4 and the land below it — are already land.
  2. 2Water there would be a single cell of sea with no route to any other, and the sea has to be one connected region.
  3. 3It can't be sea, so it's land.
4 1 3
  • Island (land)
  • Sea
  • Cells that establish the pattern
  • Where the conclusion lands
Next in the ladder Counting the Sea →

The sea's total size is fixed from the start: the whole board minus the sum of every clue. Once the marked sea reaches that count, every remaining blank is land — and once marked land reaches the clue total, every blank is sea.