diff --git a/src/fibgrid/realization.py b/src/fibgrid/realization.py
index 1d25ae5..c797672 100644
--- a/src/fibgrid/realization.py
+++ b/src/fibgrid/realization.py
@@ -138,4 +138,8 @@ def __init__(self, res, geodatum='WGS84'):
 
         lon, lat, cell, gpi, self.metadata = read_grid_file(
             n, geodatum=geodatum)
-        super().__init__(lon, lat, cell, gpi, geodatum=geodatum)
+
+        subset = np.nonzero((self.metadata['land_mask_hw'] > 50) &
+                            (self.metadata['land_mask_fw'] > 50))[0]
+
+        super().__init__(lon, lat, cell, gpi, subset=subset, geodatum=geodatum)