Index: DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfile1DTests.cs
===================================================================
diff -u -r4906 -r4927
--- DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfile1DTests.cs	(.../SoilProfile1DTests.cs)	(revision 4906)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfile1DTests.cs	(.../SoilProfile1DTests.cs)	(revision 4927)
@@ -42,7 +42,7 @@
         SoilProfile1D soilProfile1D = CreateProfileWith3Layers(true, false, true);
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Is.Null);
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Is.Empty);
             Assert.That(soilProfile1D.InBetweenAquiferLayer, Is.Null);
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer3));
             Assert.That(soilProfile1D.BottomAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer4));
@@ -52,7 +52,7 @@
         soilProfile1D = CreateProfileWith6Layers(true, true, false, false, true, true);
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Is.Null);
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Is.Empty);
             Assert.That(soilProfile1D.InBetweenAquiferLayer, Is.Null);
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer5));
             Assert.That(soilProfile1D.BottomAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer6));
@@ -62,7 +62,7 @@
         soilProfile1D = CreateProfileWith6Layers(true, true, true, true, true, true);
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Is.Null);
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Is.Empty);
             Assert.That(soilProfile1D.InBetweenAquiferLayer, Is.Null);
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer1));
             Assert.That(soilProfile1D.BottomAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer2));
@@ -72,7 +72,7 @@
         soilProfile1D = CreateProfileWith6Layers(false, false, false, false, false, false);
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Is.Null);
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Is.Empty);
             Assert.That(soilProfile1D.InBetweenAquiferLayer, Is.Null);
             Assert.That(soilProfile1D.BottomAquiferLayer, Is.Null);
         });
@@ -81,7 +81,7 @@
         soilProfile1D = CreateProfileWith6Layers(true, false, true, true, true, true);
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Is.Null);
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Is.Empty);
             Assert.That(soilProfile1D.InBetweenAquiferLayer, Is.Null);
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer3));
             Assert.That(soilProfile1D.BottomAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer4));
@@ -91,21 +91,21 @@
         soilProfile1D = CreateProfileWith6Layers(false, false, false, true, true, true);
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Is.Null);
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Is.Empty);
             Assert.That(soilProfile1D.InBetweenAquiferLayer, Is.Null);
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer4));
             Assert.That(soilProfile1D.BottomAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer5));
         });
 
         // 2 in-between aquifers present (layers 2 and 4) and bottom aquifer is the lowest layer
         soilProfile1D = CreateProfileWith6Layers(false, true, false, true, false, true);
-        Assert.That(soilProfile1D.InBetweenAquiferClusters, Has.Count.EqualTo(2));
+        Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Has.Count.EqualTo(2));
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(topLevelLayer2));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(topLevelLayer3));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[1].Item1.TopLevel, Is.EqualTo(topLevelLayer4));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[1].Item2.BottomLevel, Is.EqualTo(topLevelLayer5));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(topLevelLayer2));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(topLevelLayer3));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[1].Item1.TopLevel, Is.EqualTo(topLevelLayer4));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[1].Item2.BottomLevel, Is.EqualTo(topLevelLayer5));
             Assert.That(soilProfile1D.InBetweenAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer2));
             Assert.That(soilProfile1D.InBetweenAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer3));
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer6));
@@ -114,11 +114,11 @@
 
         // 1 in-between aquifers cluster present (layers 2-4) and bottom aquifer is the lowest layer
         soilProfile1D = CreateProfileWith6Layers(false, true, true, true, false, true);
-        Assert.That(soilProfile1D.InBetweenAquiferClusters, Has.Count.EqualTo(1));
+        Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Has.Count.EqualTo(1));
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(topLevelLayer2));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(topLevelLayer5));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(topLevelLayer2));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(topLevelLayer5));
             Assert.That(soilProfile1D.InBetweenAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer2));
             Assert.That(soilProfile1D.InBetweenAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer3));
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer6));
@@ -127,11 +127,11 @@
 
         // 1 in-between aquifer present (layer 2) and bottom aquifer is the highest layer of cluster 4-6
         soilProfile1D = CreateProfileWith6Layers(false, true, false, true, true, true);
-        Assert.That(soilProfile1D.InBetweenAquiferClusters, Has.Count.EqualTo(1));
+        Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Has.Count.EqualTo(1));
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(topLevelLayer2));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(topLevelLayer3));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(topLevelLayer2));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(topLevelLayer3));
             Assert.That(soilProfile1D.InBetweenAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer2));
             Assert.That(soilProfile1D.InBetweenAquiferLayer.BottomLevel, Is.EqualTo(topLevelLayer3));
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(topLevelLayer4));
Index: DamEngine/trunk/src/Deltares.DamEngine.Data/Geotechnics/SoilProfile1D.cs
===================================================================
diff -u -r4909 -r4927
--- DamEngine/trunk/src/Deltares.DamEngine.Data/Geotechnics/SoilProfile1D.cs	(.../SoilProfile1D.cs)	(revision 4909)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data/Geotechnics/SoilProfile1D.cs	(.../SoilProfile1D.cs)	(revision 4927)
@@ -205,26 +205,25 @@
     /// <value>
     /// The list of all clusters of in-between aquifers.
     /// </value>
-    public IList<(SoilLayer1D, SoilLayer1D)> InBetweenAquiferClusters
+    public IList<(SoilLayer1D, SoilLayer1D)> GetInBetweenAquiferClusters => InBetweenAquiferClusters();
+    
+    private IList<(SoilLayer1D, SoilLayer1D)> InBetweenAquiferClusters()
     {
-        get
+        // At least 4 layers are needed (aquitard, aquifer, aquitard, aquifer) to get one in-between aquifer
+        if (LayerCount <= 3)
         {
-            // At least 4 layers are needed (aquitard, aquifer, aquitard, aquifer) to get one in-between aquifer
-            if (LayerCount <= 3)
-            {
-                return null;
-            }
+            return new List<(SoilLayer1D, SoilLayer1D)>();
+        }
 
-            IList<SoilLayer1D> sortedLayers = Layers.OrderByDescending(l => l.TopLevel).ToList();
-            IList<SoilLayer1D> topLayers = DetermineTopLayersOfInBetweenAquiferClusters(sortedLayers);
-            if (topLayers.Count <= 0)
-            {
-                return null;
-            }
-
-            IList<SoilLayer1D> bottomLayers = DetermineBottomLayersOfInBetweenAquiferClusters(sortedLayers, layers.IndexOf(topLayers.First()));
-            return topLayers.Count != bottomLayers.Count ? null : topLayers.Select((topLayer, i) => new ValueTuple<SoilLayer1D, SoilLayer1D>(topLayer, bottomLayers[i])).ToList();
+        IList<SoilLayer1D> sortedLayers = Layers.OrderByDescending(l => l.TopLevel).ToList();
+        IList<SoilLayer1D> topLayers = DetermineTopLayersOfInBetweenAquiferClusters(sortedLayers);
+        if (topLayers.Count <= 0)
+        {
+            return new List<(SoilLayer1D, SoilLayer1D)>();
         }
+
+        IList<SoilLayer1D> bottomLayers = DetermineBottomLayersOfInBetweenAquiferClusters(sortedLayers, layers.IndexOf(topLayers.First()));
+        return topLayers.Count != bottomLayers.Count ? null : topLayers.Select((topLayer, i) => new ValueTuple<SoilLayer1D, SoilLayer1D>(topLayer, bottomLayers[i])).ToList();
     }
 
     /// <summary>
@@ -238,7 +237,7 @@
     {
         get
         {
-            return InBetweenAquiferClusters?.First().Item1;
+            return GetInBetweenAquiferClusters.Count == 0 ? null : GetInBetweenAquiferClusters.First().Item1;
         }
     }
 
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/PlLinesToWaternetConverter.cs
===================================================================
diff -u -r4920 -r4927
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/PlLinesToWaternetConverter.cs	(.../PlLinesToWaternetConverter.cs)	(revision 4920)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/PlLinesToWaternetConverter.cs	(.../PlLinesToWaternetConverter.cs)	(revision 4927)
@@ -200,9 +200,9 @@
         if (headLine != null && !IsBelowSoilProfile(soilProfile1D, plLine))
         {
             waternet.HeadLineList.Add(headLine);
-            if (soilProfile1D.InBetweenAquiferClusters != null)
+            if (soilProfile1D.GetInBetweenAquiferClusters != null)
             {
-                foreach ((SoilLayer1D, SoilLayer1D) inBetweenAquiferCluster in soilProfile1D.InBetweenAquiferClusters.Where(layer => layer is { Item1: not null, Item2: not null }))
+                foreach ((SoilLayer1D, SoilLayer1D) inBetweenAquiferCluster in soilProfile1D.GetInBetweenAquiferClusters.Where(layer => layer is { Item1: not null, Item2: not null }))
                 {
                     double levelTop = inBetweenAquiferCluster.Item1.TopLevel;
                     double levelBottom = inBetweenAquiferCluster.Item2.BottomLevel;
@@ -254,7 +254,7 @@
         for (var i = 0; i < xCoordinates.Length; i++)
         {
             SoilProfile1D crossSection = soilProfile.GetSoilProfile1D(xCoordinates[i]);
-            currentCount = crossSection.InBetweenAquiferClusters?.Count ?? 0;
+            currentCount = crossSection.GetInBetweenAquiferClusters?.Count ?? 0;
             if (i > 0 && currentCount != previousCount)
             {
                 return 0;
@@ -415,9 +415,9 @@
             case LayerType.BottomAquifer:
                 return soilProfile1D.BottomAquiferLayer;
             case LayerType.TopLayerInBetweenAquiferCluster:
-                return soilProfile1D.InBetweenAquiferClusters[indexInBetweenAquifer].Item1;
+                return soilProfile1D.GetInBetweenAquiferClusters[indexInBetweenAquifer].Item1;
             case LayerType.BottomLayerInBetweenAquiferCluster:
-                return soilProfile1D.InBetweenAquiferClusters[indexInBetweenAquifer].Item2;
+                return soilProfile1D.GetInBetweenAquiferClusters[indexInBetweenAquifer].Item2;
         }
 
         return null;
@@ -623,14 +623,14 @@
     private static List<Line> DivideCurvesIntoLines(List<GeometryPointString> curves)
     {
         var lines = new List<Line>();
-        foreach (GeometryPointString curve in curves)
+        foreach (IList<GeometryPoint> points in curves.Select(curve => curve.Points))
         {
-            for (var i = 0; i < curve.Points.Count - 1; i++)
+            for (var i = 0; i < points.Count - 1; i++)
             {
                 var line = new Line
                 {
-                    BeginPoint = new Point2D(curve.Points[i].X, curve.Points[i].Z),
-                    EndPoint = new Point2D(curve.Points[i + 1].X, curve.Points[i + 1].Z)
+                    BeginPoint = new Point2D(points[i].X, points[i].Z),
+                    EndPoint = new Point2D(points[i + 1].X, points[i + 1].Z)
                 };
                 lines.Add(line);
             }
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators.Tests/KernelWrappers/MacroStabilityCommon/PlLinesToWaternetConverterTests.cs
===================================================================
diff -u -r4909 -r4927
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators.Tests/KernelWrappers/MacroStabilityCommon/PlLinesToWaternetConverterTests.cs	(.../PlLinesToWaternetConverterTests.cs)	(revision 4909)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators.Tests/KernelWrappers/MacroStabilityCommon/PlLinesToWaternetConverterTests.cs	(.../PlLinesToWaternetConverterTests.cs)	(revision 4927)
@@ -88,11 +88,11 @@
         SoilProfile1D soilProfile1D = CreateSoilProfile1DForTest();
         Assert.Multiple(() =>
         {
-            Assert.That(soilProfile1D.InBetweenAquiferClusters, Has.Count.EqualTo(2).Within(precision3Decimals));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(-2.111).Within(precision3Decimals));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(-3.373).Within(precision3Decimals));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[1].Item1.TopLevel, Is.EqualTo(-4.151).Within(precision3Decimals));
-            Assert.That(soilProfile1D.InBetweenAquiferClusters[1].Item2.BottomLevel, Is.EqualTo(-5.373).Within(precision3Decimals));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters, Has.Count.EqualTo(2).Within(precision3Decimals));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item1.TopLevel, Is.EqualTo(-2.111).Within(precision3Decimals));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[0].Item2.BottomLevel, Is.EqualTo(-3.373).Within(precision3Decimals));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[1].Item1.TopLevel, Is.EqualTo(-4.151).Within(precision3Decimals));
+            Assert.That(soilProfile1D.GetInBetweenAquiferClusters[1].Item2.BottomLevel, Is.EqualTo(-5.373).Within(precision3Decimals));
             Assert.That(soilProfile1D.BottomAquiferLayer.TopLevel, Is.EqualTo(-6.111).Within(precision3Decimals));
         });