diff --git a/src/definition/DefinitionNode.cpp b/src/definition/DefinitionNode.cpp
index 2c89a98..a6c44db 100644
--- a/src/definition/DefinitionNode.cpp
+++ b/src/definition/DefinitionNode.cpp
@@ -2,6 +2,7 @@
 
 #include "Logs.h"
 #include "PackStream.h"
+#include "DefinitionWatcher.h"
 #include "DefinitionDiff.h"
 #include "DiffManager.h"
 
@@ -157,10 +158,25 @@ bool DefinitionNode::applyDiff(const DefinitionDiff *diff, bool)
     }
 }
 
-void DefinitionNode::addWatcher(DefinitionWatcher *watcher)
+void DefinitionNode::generateInitDiffs(std::vector<const DefinitionDiff *> *) const
+{
+}
+
+void DefinitionNode::addWatcher(DefinitionWatcher *watcher, bool init_diff)
 {
     if (root && root->diffs)
     {
+        if (init_diff)
+        {
+            std::vector<const DefinitionDiff *> diffs;
+            generateInitDiffs(&diffs);
+
+            for (auto diff: diffs)
+            {
+                watcher->nodeChanged(this, diff);
+                delete diff;
+            }
+        }
         root->diffs->addWatcher(this, watcher);
     }
 }
diff --git a/src/definition/DefinitionNode.h b/src/definition/DefinitionNode.h
index b6363ab..5fb3307 100644
--- a/src/definition/DefinitionNode.h
+++ b/src/definition/DefinitionNode.h
@@ -61,12 +61,21 @@ public:
      */
     virtual bool applyDiff(const DefinitionDiff *diff, bool backward=false);
 
+    /**
+     * Fill a diff array to be applied to initialize a proper state for a watcher.
+     *
+     * This method should be overridden by subclasses.
+     */
+    virtual void generateInitDiffs(std::vector<const DefinitionDiff *> *diffs) const;
+
     /**
      * Add a watcher over this node.
      *
      * The watcher will receive DefinitionDiff objects when this node changes.
+     *
+     * If *init_diff* is set to true, a first diff (or several) will be be pushed immediately to initialize the state.
      */
-    void addWatcher(DefinitionWatcher *watcher);
+    void addWatcher(DefinitionWatcher *watcher, bool init_diff=false);
 
 protected:
     void addChild(DefinitionNode* child);
diff --git a/src/definition/DefinitionWatcher.h b/src/definition/DefinitionWatcher.h
index 1a6217c..b209e69 100644
--- a/src/definition/DefinitionWatcher.h
+++ b/src/definition/DefinitionWatcher.h
@@ -15,6 +15,11 @@ class DEFINITIONSHARED_EXPORT DefinitionWatcher
 {
 public:
     DefinitionWatcher();
+
+    /**
+     * Abstract method called when a node changed.
+     */
+    virtual void nodeChanged(const DefinitionNode *node, const DefinitionDiff *diff) = 0;
 };
 
 }
diff --git a/src/definition/DiffManager.cpp b/src/definition/DiffManager.cpp
index 385afda..ea8ce25 100644
--- a/src/definition/DiffManager.cpp
+++ b/src/definition/DiffManager.cpp
@@ -2,6 +2,7 @@
 
 #include "DefinitionNode.h"
 #include "DefinitionDiff.h"
+#include "DefinitionWatcher.h"
 
 DiffManager::DiffManager(DefinitionNode *tree):
     tree(tree)
@@ -9,6 +10,15 @@ DiffManager::DiffManager(DefinitionNode *tree):
     undone = 0;
 }
 
+DiffManager::~DiffManager()
+{
+    for (auto diff: diffs)
+    {
+        delete diff;
+    }
+    diffs.clear();
+}
+
 void DiffManager::addWatcher(const DefinitionNode *node, DefinitionWatcher *watcher)
 {
     watchers[node].push_back(watcher);
@@ -19,6 +29,7 @@ void DiffManager::addDiff(DefinitionNode *node, const DefinitionDiff *diff)
     while (undone > 0)
     {
         // truncate diffs ahead
+        delete diffs.back();
         diffs.pop_back();
         undone--;
     }
@@ -28,9 +39,9 @@ void DiffManager::addDiff(DefinitionNode *node, const DefinitionDiff *diff)
     // TODO Delayed commit (with merge of consecutive diffs)
     node->applyDiff(diff);
 
-    for (auto &watcher: watchers[node])
+    for (auto watcher: watchers[node])
     {
-        // TODO
+        watcher->nodeChanged(node, diff);
     }
 }
 
diff --git a/src/definition/DiffManager.h b/src/definition/DiffManager.h
index 7af1b26..f0998ce 100644
--- a/src/definition/DiffManager.h
+++ b/src/definition/DiffManager.h
@@ -18,6 +18,7 @@ class DEFINITIONSHARED_EXPORT DiffManager
 {
 public:
     DiffManager(DefinitionNode *tree);
+    ~DiffManager();
 
     /**
      * Add a watcher for a specific node.
diff --git a/src/definition/FloatNode.cpp b/src/definition/FloatNode.cpp
index 94daeda..2bca647 100644
--- a/src/definition/FloatNode.cpp
+++ b/src/definition/FloatNode.cpp
@@ -52,6 +52,11 @@ const FloatDiff *FloatNode::produceDiff(double new_value) const
     return new FloatDiff(this, value, new_value);
 }
 
+void FloatNode::generateInitDiffs(std::vector<const DefinitionDiff *> *diffs) const
+{
+    diffs->push_back(produceDiff(value));
+}
+
 bool FloatNode::applyDiff(const DefinitionDiff *diff, bool backward)
 {
     if (!DefinitionNode::applyDiff(diff, backward))
diff --git a/src/definition/FloatNode.h b/src/definition/FloatNode.h
index dba95d8..6a8bb68 100644
--- a/src/definition/FloatNode.h
+++ b/src/definition/FloatNode.h
@@ -30,6 +30,7 @@ public:
      */
     void setValue(double new_value);
     const FloatDiff *produceDiff(double new_value) const;
+    void generateInitDiffs(std::vector<const DefinitionDiff *> *diffs) const;
     virtual bool applyDiff(const DefinitionDiff *diff, bool backward=false) override;
 private:
     double value;
diff --git a/src/definition/TerrainDefinition.cpp b/src/definition/TerrainDefinition.cpp
index 8ac68a6..ef00cc1 100644
--- a/src/definition/TerrainDefinition.cpp
+++ b/src/definition/TerrainDefinition.cpp
@@ -15,8 +15,7 @@ TerrainDefinition::TerrainDefinition(DefinitionNode* parent):
     height_map = new TerrainHeightMap(this);
     addChild(height_map);
 
-    water_height = -0.3;
-    _water_height = new FloatNode(this, "water_height", -0.3);
+    water_height = new FloatNode(this, "water_height", -0.3);
 
     _height_noise = new NoiseGenerator;
 }
@@ -67,7 +66,6 @@ void TerrainDefinition::save(PackStream* stream) const
     stream->write(&height);
     stream->write(&scaling);
     stream->write(&shadow_smoothing);
-    stream->write(&water_height);
     _height_noise->save(stream);
 }
 
@@ -78,7 +76,6 @@ void TerrainDefinition::load(PackStream* stream)
     stream->read(&height);
     stream->read(&scaling);
     stream->read(&shadow_smoothing);
-    stream->read(&water_height);
     _height_noise->load(stream);
 
     validate();
@@ -96,7 +93,7 @@ double TerrainDefinition::getGridHeight(int x, int z, bool with_painting)
     return h;
 }
 
-double TerrainDefinition::getInterpolatedHeight(double x, double z, bool scaled, bool with_painting)
+double TerrainDefinition::getInterpolatedHeight(double x, double z, bool scaled, bool with_painting, bool water_offset)
 {
     double h;
     x /= scaling;
@@ -109,7 +106,7 @@ double TerrainDefinition::getInterpolatedHeight(double x, double z, bool scaled,
 
     if (scaled)
     {
-        return (h - water_height) * height * scaling;
+        return (water_offset ? (h - water_height->getValue()) : h) * height * scaling;
     }
     else
     {
@@ -117,6 +114,11 @@ double TerrainDefinition::getInterpolatedHeight(double x, double z, bool scaled,
     }
 }
 
+double TerrainDefinition::getWaterOffset() const
+{
+    return -water_height->getValue() * height * scaling;
+}
+
 HeightInfo TerrainDefinition::getHeightInfo()
 {
     HeightInfo result;
@@ -124,7 +126,7 @@ HeightInfo TerrainDefinition::getHeightInfo()
     result.min_height = _min_height;
     result.max_height = _max_height;
     /* TODO This is duplicated in ter_render.c (_realGetWaterHeight) */
-    result.base_height = water_height * height * scaling;
+    result.base_height = water_height->getValue() * height * scaling;
 
     return result;
 }
diff --git a/src/definition/TerrainDefinition.h b/src/definition/TerrainDefinition.h
index 626d8ea..27bcc2f 100644
--- a/src/definition/TerrainDefinition.h
+++ b/src/definition/TerrainDefinition.h
@@ -27,8 +27,11 @@ public:
     virtual void copy(DefinitionNode* destination) const override;
     virtual void validate() override;
 
+    inline FloatNode *propWaterHeight() const {return water_height;}
+
     double getGridHeight(int x, int z, bool with_painting);
-    double getInterpolatedHeight(double x, double z, bool scaled, bool with_painting);
+    double getInterpolatedHeight(double x, double z, bool scaled, bool with_painting, bool water_offset=true);
+    double getWaterOffset() const;
     unsigned long getMemoryStats();
     HeightInfo getHeightInfo();
 
@@ -46,15 +49,13 @@ public:
 
     TerrainHeightMap* height_map;
 
-    double water_height;
-
     double _detail;
     NoiseGenerator* _height_noise;
     double _min_height;
     double _max_height;
 
 private:
-    FloatNode *_water_height;
+    FloatNode *water_height;
 };
 
 }
diff --git a/src/interface/modeler/quickapp/MainModelerWindow.cpp b/src/interface/modeler/quickapp/MainModelerWindow.cpp
index 947a9d8..d8494ca 100644
--- a/src/interface/modeler/quickapp/MainModelerWindow.cpp
+++ b/src/interface/modeler/quickapp/MainModelerWindow.cpp
@@ -10,6 +10,7 @@
 #include "RenderPreviewProvider.h"
 #include "RenderProcess.h"
 #include "RenderConfig.h"
+#include "DiffManager.h"
 
 #include <QQmlEngine>
 #include <QGuiApplication>
@@ -103,4 +104,25 @@ void MainModelerWindow::keyReleaseEvent(QKeyEvent *event)
             QGuiApplication::instance()->exit();
         }
     }
+    else if (event->key() == Qt::Key_Z)
+    {
+        if (event->modifiers() & Qt::ControlModifier)
+        {
+            if (event->modifiers() & Qt::ShiftModifier)
+            {
+                scenery->getDiffManager()->redo();
+            }
+            else
+            {
+                scenery->getDiffManager()->undo();
+            }
+        }
+    }
+    else if (event->key() == Qt::Key_Y)
+    {
+        if (event->modifiers() & Qt::ControlModifier)
+        {
+            scenery->getDiffManager()->undo();
+        }
+    }
 }
diff --git a/src/interface/modeler/quickapp/WaterModeler.cpp b/src/interface/modeler/quickapp/WaterModeler.cpp
index f54960a..4a497a0 100644
--- a/src/interface/modeler/quickapp/WaterModeler.cpp
+++ b/src/interface/modeler/quickapp/WaterModeler.cpp
@@ -1,6 +1,10 @@
 #include "WaterModeler.h"
 
 #include "MainModelerWindow.h"
+#include "Scenery.h"
+#include "TerrainDefinition.h"
+#include "FloatNode.h"
+#include "Logs.h"
 
 WaterModeler::WaterModeler(MainModelerWindow *main):
     main(main)
@@ -8,12 +12,17 @@ WaterModeler::WaterModeler(MainModelerWindow *main):
     QObject *item = main->findQmlObject("water_level");
     if (item)
     {
+        item->setProperty("value", propWaterHeight()->getValue() * 0.5 + 0.5);
         connect(item, SIGNAL(changed(double)), this, SLOT(waterLevelChanged(double)));
     }
 }
 
-void WaterModeler::waterLevelChanged(double)
+void WaterModeler::waterLevelChanged(double value)
 {
-    // TODO
-    //qDebug() << "water level : " << value;
+    propWaterHeight()->setValue(value * 2.0 - 1.0);
+}
+
+FloatNode *WaterModeler::propWaterHeight() const
+{
+    return main->getScenery()->getTerrain()->propWaterHeight();
 }
diff --git a/src/interface/modeler/quickapp/WaterModeler.h b/src/interface/modeler/quickapp/WaterModeler.h
index fac513e..ceb2b10 100644
--- a/src/interface/modeler/quickapp/WaterModeler.h
+++ b/src/interface/modeler/quickapp/WaterModeler.h
@@ -18,6 +18,7 @@ public slots:
     void waterLevelChanged(double value);
 
 private:
+    FloatNode *propWaterHeight() const;
     MainModelerWindow *main;
 };
 
diff --git a/src/render/opengl/ExplorerChunkTerrain.cpp b/src/render/opengl/ExplorerChunkTerrain.cpp
index 2d9f297..baaca0a 100644
--- a/src/render/opengl/ExplorerChunkTerrain.cpp
+++ b/src/render/opengl/ExplorerChunkTerrain.cpp
@@ -9,7 +9,7 @@
 #include "TerrainRenderer.h"
 #include "VertexArray.h"
 
-ExplorerChunkTerrain::ExplorerChunkTerrain(OpenGLRenderer* renderer, double x, double z, double size, int nbchunks, double water_height):
+ExplorerChunkTerrain::ExplorerChunkTerrain(OpenGLRenderer* renderer, double x, double z, double size, int nbchunks):
     _renderer(renderer)
 {
     priority = 0.0;
@@ -32,7 +32,6 @@ ExplorerChunkTerrain::ExplorerChunkTerrain(OpenGLRenderer* renderer, double x, d
 
     distance_to_camera = 0.0;
 
-    _water_height = water_height;
     overwater = false;
 
     tessellation_count = 33;
@@ -90,8 +89,8 @@ bool ExplorerChunkTerrain::maintain()
                         double x = _startx + _tessellation_step * (float)i;
                         double z = _startz + _tessellation_step * (float)j;
 
-                        double height = _renderer->getTerrainRenderer()->getHeight(x, z, true);
-                        if (height >= _water_height)
+                        double height = _renderer->getTerrainRenderer()->getHeight(x, z, true, false);
+                        if (height >= 0.0)
                         {
                             overwater = true;
                         }
@@ -270,7 +269,7 @@ void ExplorerChunkTerrain::render(QOpenGLShaderProgram* program, OpenGLFunctions
         int tessellation_size = _tessellation_current_size;
         _lock_data.unlock();
 
-        if (tessellation_size <= 1 or not overwater)
+        if (tessellation_size <= 1)
         {
             return;
         }
diff --git a/src/render/opengl/ExplorerChunkTerrain.h b/src/render/opengl/ExplorerChunkTerrain.h
index 6402299..cc8d420 100644
--- a/src/render/opengl/ExplorerChunkTerrain.h
+++ b/src/render/opengl/ExplorerChunkTerrain.h
@@ -20,7 +20,7 @@ public:
     } TerrainVertex;
 
 public:
-    ExplorerChunkTerrain(OpenGLRenderer* renderer, double x, double z, double size, int nbchunks, double water_height);
+    ExplorerChunkTerrain(OpenGLRenderer* renderer, double x, double z, double size, int nbchunks);
     ~ExplorerChunkTerrain();
 
     bool maintain();
@@ -42,8 +42,6 @@ private:
     double _size;
     double _overall_step;
 
-    double _water_height;
-
     int tessellation_count;
     VertexArray<TerrainVertex> *tessellated;
     int _tessellation_max_size;
diff --git a/src/render/opengl/OpenGLTerrain.cpp b/src/render/opengl/OpenGLTerrain.cpp
index a6c7ec9..dfce72c 100644
--- a/src/render/opengl/OpenGLTerrain.cpp
+++ b/src/render/opengl/OpenGLTerrain.cpp
@@ -9,6 +9,8 @@
 #include "WaterRenderer.h"
 #include "CameraDefinition.h"
 #include "Scenery.h"
+#include "FloatNode.h"
+#include "FloatDiff.h"
 
 class ChunkMaintenanceThreads:public ParallelPool
 {
@@ -62,12 +64,11 @@ void OpenGLTerrain::initialize()
     double size = 800.0;
     double chunksize = size / (double) chunks;
     double start = -size / 2.0;
-    double water_height = renderer->getWaterRenderer()->getHeightInfo().base_height;
     for (int i = 0; i < chunks; i++)
     {
         for (int j = 0; j < chunks; j++)
         {
-            ExplorerChunkTerrain* chunk = new ExplorerChunkTerrain(renderer, start + chunksize * (double) i, start + chunksize * (double) j, chunksize, chunks, water_height);
+            ExplorerChunkTerrain* chunk = new ExplorerChunkTerrain(renderer, start + chunksize * (double) i, start + chunksize * (double) j, chunksize, chunks);
             _chunks.append(chunk);
             _updateQueue.append(chunk);
         }
@@ -75,6 +76,9 @@ void OpenGLTerrain::initialize()
 
     // Start chunks maintenance
     work->start();
+
+    // Watch for definition changes
+    renderer->getScenery()->getTerrain()->propWaterHeight()->addWatcher(this);
 }
 
 void OpenGLTerrain::update()
@@ -142,3 +146,12 @@ void OpenGLTerrain::performChunksMaintenance()
     qSort(_updateQueue.begin(), _updateQueue.end(), _cmpChunks);
     _lock_chunks.unlock();
 }
+
+
+void OpenGLTerrain::nodeChanged(const DefinitionNode *node, const DefinitionDiff *)
+{
+    if (node->getPath() == "/terrain/water_height")
+    {
+        resetTextures();
+    }
+}
diff --git a/src/render/opengl/OpenGLTerrain.h b/src/render/opengl/OpenGLTerrain.h
index a888f5e..fa6cbec 100644
--- a/src/render/opengl/OpenGLTerrain.h
+++ b/src/render/opengl/OpenGLTerrain.h
@@ -4,6 +4,7 @@
 #include "opengl_global.h"
 
 #include "OpenGLPart.h"
+#include "DefinitionWatcher.h"
 
 #include <QVector>
 #include <QList>
@@ -12,7 +13,7 @@
 namespace paysages {
 namespace opengl {
 
-class OPENGLSHARED_EXPORT OpenGLTerrain:public OpenGLPart
+class OPENGLSHARED_EXPORT OpenGLTerrain: public OpenGLPart, public DefinitionWatcher
 {
 public:
     OpenGLTerrain(OpenGLRenderer* renderer);
@@ -30,6 +31,7 @@ public:
 
     void performChunksMaintenance();
 
+    virtual void nodeChanged(const DefinitionNode *node, const DefinitionDiff *diff) override;
 private:
     OpenGLShaderProgram* program;
 
@@ -38,6 +40,7 @@ private:
     QVector<ExplorerChunkTerrain*> _chunks;
     QList<ExplorerChunkTerrain*> _updateQueue;
     QMutex _lock_chunks;
+
 };
 
 }
diff --git a/src/render/opengl/OpenGLWater.cpp b/src/render/opengl/OpenGLWater.cpp
index 88f6a00..111e5e1 100644
--- a/src/render/opengl/OpenGLWater.cpp
+++ b/src/render/opengl/OpenGLWater.cpp
@@ -8,6 +8,8 @@
 #include "WaterDefinition.h"
 #include "SurfaceMaterial.h"
 #include "NoiseFunctionSimplex.h"
+#include "FloatNode.h"
+#include "FloatDiff.h"
 
 OpenGLWater::OpenGLWater(OpenGLRenderer *renderer):
     OpenGLPart(renderer)
@@ -34,6 +36,9 @@ void OpenGLWater::initialize()
     setVertex(1, -1.0f, 0.0f, 1.0f);
     setVertex(2, 1.0f, 0.0f, -1.0f);
     setVertex(3, 1.0f, 0.0f, 1.0f);
+
+    // Watch for definition changes
+    renderer->getScenery()->getTerrain()->propWaterHeight()->addWatcher(this, true);
 }
 
 void OpenGLWater::update()
@@ -58,3 +63,11 @@ void OpenGLWater::setVertex(int i, float x, float y, float z)
     vertices[i * 3 + 1] = y;
     vertices[i * 3 + 2] = z;
 }
+
+void OpenGLWater::nodeChanged(const DefinitionNode *node, const DefinitionDiff *)
+{
+    if (node->getPath() == "/terrain/water_height")
+    {
+        renderer->getSharedState()->set("waterOffset", renderer->getScenery()->getTerrain()->getWaterOffset());
+    }
+}
diff --git a/src/render/opengl/OpenGLWater.h b/src/render/opengl/OpenGLWater.h
index a30d4bc..c64ae2e 100644
--- a/src/render/opengl/OpenGLWater.h
+++ b/src/render/opengl/OpenGLWater.h
@@ -4,11 +4,12 @@
 #include "opengl_global.h"
 
 #include "OpenGLPart.h"
+#include "DefinitionWatcher.h"
 
 namespace paysages {
 namespace opengl {
 
-class OPENGLSHARED_EXPORT OpenGLWater: public OpenGLPart
+class OPENGLSHARED_EXPORT OpenGLWater: public OpenGLPart, public DefinitionWatcher
 {
 public:
     OpenGLWater(OpenGLRenderer* renderer);
@@ -18,6 +19,7 @@ public:
     virtual void update() override;
     virtual void render() override;
 
+    virtual void nodeChanged(const DefinitionNode *node, const DefinitionDiff *diff) override;
 private:
     void setVertex(int i, float x, float y, float z);
 
diff --git a/src/render/opengl/shaders/terrain.vert b/src/render/opengl/shaders/terrain.vert
index c4fd270..697e1e0 100644
--- a/src/render/opengl/shaders/terrain.vert
+++ b/src/render/opengl/shaders/terrain.vert
@@ -3,10 +3,12 @@ attribute highp vec2 uv;
 uniform highp mat4 viewMatrix;
 varying vec3 unprojected;
 varying vec2 texcoord;
+uniform float waterOffset;
 
 void main(void)
 {
-    unprojected = vertex.xyz;
+    vec4 final = vertex + vec4(0, waterOffset, 0, 0);
+    unprojected = final.xyz;
     texcoord = uv;
-    gl_Position = viewMatrix * vertex;
+    gl_Position = viewMatrix * final;
 }
diff --git a/src/render/software/TerrainRenderer.cpp b/src/render/software/TerrainRenderer.cpp
index a087b36..1e5ecb3 100644
--- a/src/render/software/TerrainRenderer.cpp
+++ b/src/render/software/TerrainRenderer.cpp
@@ -23,9 +23,9 @@ void TerrainRenderer::update()
     walker->update();
 }
 
-double TerrainRenderer::getHeight(double x, double z, bool with_painting)
+double TerrainRenderer::getHeight(double x, double z, bool with_painting, bool water_offset)
 {
-    return parent->getScenery()->getTerrain()->getInterpolatedHeight(x, z, true, with_painting);
+    return parent->getScenery()->getTerrain()->getInterpolatedHeight(x, z, true, with_painting, water_offset);
 }
 
 static inline Vector3 _getNormal4(Vector3 center, Vector3 north, Vector3 east, Vector3 south, Vector3 west)
diff --git a/src/render/software/TerrainRenderer.h b/src/render/software/TerrainRenderer.h
index 529e1ed..7301ae0 100644
--- a/src/render/software/TerrainRenderer.h
+++ b/src/render/software/TerrainRenderer.h
@@ -27,7 +27,7 @@ public:
     virtual void update();
 
     virtual RayCastingResult castRay(const Vector3 &start, const Vector3 &direction);
-    virtual double getHeight(double x, double z, bool with_painting);
+    virtual double getHeight(double x, double z, bool with_painting, bool water_offset=true);
     virtual TerrainResult getResult(double x, double z, bool with_painting, bool with_textures);
     virtual Color getFinalColor(const Vector3 &location, double precision);
     virtual bool applyLightFilter(LightComponent &light, const Vector3 &at) override;
diff --git a/src/tests/DiffManager_Test.cpp b/src/tests/DiffManager_Test.cpp
index 4e60b5e..332aed3 100644
--- a/src/tests/DiffManager_Test.cpp
+++ b/src/tests/DiffManager_Test.cpp
@@ -2,6 +2,8 @@
 
 #include "DiffManager.h"
 #include "DefinitionNode.h"
+#include "DefinitionWatcher.h"
+#include "FloatDiff.h"
 #include "FloatNode.h"
 
 TEST(DiffManager, undoRedo)
@@ -111,3 +113,52 @@ TEST(DiffManager, undoBranch)
     diffs->redo();
     EXPECT_DOUBLE_EQ(4.4, leaf.getValue());
 }
+
+class TestWatcher: public DefinitionWatcher
+{
+public:
+    TestWatcher(DefinitionNode* expected_node, double expected_old_value, double expected_new_value):
+        DefinitionWatcher(), expected_node(expected_node), expected_old_value(expected_old_value), expected_new_value(expected_new_value)
+    {
+        calls = 0;
+    }
+
+    virtual void nodeChanged(const DefinitionNode *node, const DefinitionDiff *diff) override
+    {
+        EXPECT_EQ(expected_node, node);
+        ASSERT_EQ("float", diff->getTypeName());
+        const FloatDiff *float_diff = (const FloatDiff *)diff;
+        EXPECT_EQ(expected_old_value, float_diff->getOldValue());
+        EXPECT_EQ(expected_new_value, float_diff->getNewValue());
+        calls++;
+    }
+
+    int calls;
+    DefinitionNode* expected_node;
+    double expected_old_value;
+    double expected_new_value;
+};
+
+TEST(DiffManager, addWatcher)
+{
+    FloatNode node(NULL, "node");
+    TestWatcher watcher(&node, 1.3, -4.0);
+
+    node.setValue(1.3);
+    EXPECT_EQ(0, watcher.calls);
+
+    node.addWatcher(&watcher);
+    EXPECT_EQ(0, watcher.calls);
+
+    node.setValue(-4.0);
+    EXPECT_EQ(1, watcher.calls);
+}
+
+TEST(DiffManager, addWatcherWithInitDiffs)
+{
+    FloatNode node(NULL, "node", 1.3);
+    TestWatcher watcher(&node, 1.3, 1.3);
+
+    node.addWatcher(&watcher, true);
+    EXPECT_EQ(1, watcher.calls);
+}
diff --git a/src/tests/TerrainPainting_Test.cpp b/src/tests/TerrainPainting_Test.cpp
index 1df9b3f..ab96151 100644
--- a/src/tests/TerrainPainting_Test.cpp
+++ b/src/tests/TerrainPainting_Test.cpp
@@ -5,6 +5,7 @@
 #include "TerrainDefinition.h"
 #include "TerrainHeightMap.h"
 #include "PaintedGridBrush.h"
+#include "FloatNode.h"
 
 /* Noise sin period is defined at 20.0 */
 #define X_FACTOR (M_PI / 10.0)
@@ -31,7 +32,7 @@ protected:
         terrain->height = 3.0;
         terrain->scaling = 1.0;
         terrain->_height_noise->clearLevels();
-        terrain->water_height = 0.0;
+        terrain->propWaterHeight()->setValue(0.0);
         NoiseGenerator::NoiseLevel level = {1.0, 2.0, -1.0};
         terrain->_height_noise->addLevel(level);
         noise_state.resetOffsets();