diff --git a/isometric-park-fna/FNAGame.cs b/isometric-park-fna/FNAGame.cs
--- a/isometric-park-fna/FNAGame.cs
+++ b/isometric-park-fna/FNAGame.cs
@@ -613,8 +613,8 @@
         //Unfortunately this is tileset dependent and pretty awkward to type out :(
         var northwest = (x != 0 && (cells[x-1][y].Status == CellStatus.Water));
         var northeast = (y != 0 && (cells[x][y-1].Status == CellStatus.Water));
-        var southwest = cells[x][y+1].Status == CellStatus.Water;
-        var southeast = cells[x+1][y].Status == CellStatus.Water;
+        var southwest = (y < (this.simulation.map.MapHeight-1)  && cells[x][y+1].Status == CellStatus.Water);
+        var southeast = (x < (this.simulation.map.MapWidth-1)  && cells[x+1][y].Status == CellStatus.Water);
 
 
         if (northwest && northeast && southwest && southeast) {