Between Two Islands

Medium Used by Smart Hint

A cell touching two different islands can't belong to either one — it's sea.

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

How it works

Two different islands have grown close enough that one cell now touches both of them.
That cell can't join either island without connecting them — it must be sea. This is the general form of Diagonal Clues: it applies to any two islands' current shapes, not just their starting clue positions.