Index: ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Sections/Environment/Environment.h
===================================================================
--- ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Sections/Environment/Environment.h
+++ ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Sections/Environment/Environment.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2009 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -26,9 +26,12 @@
 public:
 	EnvironmentSidebar(ScenarioEditor& scenarioEditor, wxWindow* sidebarContainer, wxWindow* bottomBarContainer);
 
+	void OnPickWaterHeight(wxCommandEvent& evt);
 	virtual void OnMapReload();
 	virtual void RecomputeWaterData(wxCommandEvent& evt);
 
+	void UpdateEnvironmentSettings();
+
 protected:
 	virtual void OnFirstDisplay();
 
Index: ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Sections/Environment/Environment.cpp
===================================================================
--- ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Sections/Environment/Environment.cpp
+++ ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Sections/Environment/Environment.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2017 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -198,7 +198,8 @@
 //////////////////////////////////////////////////////////////////////////
 
 enum {
-	ID_RecomputeWaterData
+	ID_RecomputeWaterData,
+	ID_PickWaterHeight
 };
 static void SendToGame(const AtlasMessage::sEnvironmentSettings& settings)
 {
@@ -219,6 +220,7 @@
 	waterSizer->Add(new wxButton(scrolledWindow, ID_RecomputeWaterData, _("Reset Water Data")), wxSizerFlags().Expand());
 	waterSizer->Add(m_WaterTypeList = new VariableListBox(scrolledWindow, _("Water Type"), g_EnvironmentSettings.watertype), wxSizerFlags().Expand());
 	waterSizer->Add(new VariableSliderBox(scrolledWindow, _("Water height"), g_EnvironmentSettings.waterheight, 0.f, 1.2f), wxSizerFlags().Expand());
+	waterSizer->Add(new wxButton(scrolledWindow, ID_PickWaterHeight, _("Pick Water Height")), wxSizerFlags().Expand());
 	waterSizer->Add(new VariableSliderBox(scrolledWindow, _("Water waviness"), g_EnvironmentSettings.waterwaviness, 0.f, 10.f), wxSizerFlags().Expand());
 	waterSizer->Add(new VariableSliderBox(scrolledWindow, _("Water murkiness"), g_EnvironmentSettings.watermurkiness, 0.f, 1.f), wxSizerFlags().Expand());
 	waterSizer->Add(new VariableSliderBox(scrolledWindow, _("Wind angle"), g_EnvironmentSettings.windangle, -M_PIf, M_PIf), wxSizerFlags().Expand());
@@ -269,15 +271,21 @@
 	qry_effects.Post();
 	m_PostEffectList->SetChoices(*qry_effects.posteffects);
 
-	AtlasMessage::qGetEnvironmentSettings qry_env;
-	qry_env.Post();
-	g_EnvironmentSettings = qry_env.settings;
-
-	g_EnvironmentSettings.NotifyObservers();
+	UpdateEnvironmentSettings();
 }
 
 void EnvironmentSidebar::OnMapReload()
 {
+	UpdateEnvironmentSettings();
+}
+
+void EnvironmentSidebar::RecomputeWaterData(wxCommandEvent& WXUNUSED(evt))
+{
+	POST_COMMAND(RecalculateWaterData, (0.0f));
+}
+
+void EnvironmentSidebar::UpdateEnvironmentSettings()
+{
 	AtlasMessage::qGetEnvironmentSettings qry_env;
 	qry_env.Post();
 	g_EnvironmentSettings = qry_env.settings;
@@ -285,12 +293,13 @@
 	g_EnvironmentSettings.NotifyObservers();
 }
 
-void EnvironmentSidebar::RecomputeWaterData(wxCommandEvent& WXUNUSED(evt))
+void EnvironmentSidebar::OnPickWaterHeight(wxCommandEvent& evt)
 {
-	POST_COMMAND(RecalculateWaterData, (0.0f));
+	m_ScenarioEditor.GetToolManager().SetCurrentTool(_T("PickWaterHeight"), this);
 }
 
 BEGIN_EVENT_TABLE(EnvironmentSidebar, Sidebar)
 	EVT_BUTTON(ID_RecomputeWaterData, EnvironmentSidebar::RecomputeWaterData)
+	EVT_BUTTON(ID_PickWaterHeight, EnvironmentSidebar::OnPickWaterHeight)
 END_EVENT_TABLE();
 
Index: ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Tools/PickWaterHeight.cpp
===================================================================
--- ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Tools/PickWaterHeight.cpp
+++ ps/trunk/source/tools/atlas/AtlasUI/ScenarioEditor/Tools/PickWaterHeight.cpp
@@ -0,0 +1,72 @@
+/* Copyright (C) 2019 Wildfire Games.
+ * This file is part of 0 A.D.
+ *
+ * 0 A.D. is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 0 A.D. is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "precompiled.h"
+
+#include "Common/Tools.h"
+#include "Common/MiscState.h"
+#include "GameInterface/Messages.h"
+#include "ScenarioEditor/Sections/Environment/Environment.h"
+#include "ScenarioEditor/ScenarioEditor.h"
+
+using AtlasMessage::Position;
+
+class PickWaterHeight : public StateDrivenTool<PickWaterHeight>
+{
+	DECLARE_DYNAMIC_CLASS(PickWaterHeight);
+
+	// Uses a workaround to notify the environment settings directly, because
+	// we don't have any way to update them on the engine state change.
+	EnvironmentSidebar* m_Sidebar;
+
+public:
+	PickWaterHeight()
+		: m_Sidebar(nullptr)
+	{
+		SetState(&Waiting);
+	}
+
+	virtual void Init(void* initData, ScenarioEditor* scenarioEditor)
+	{
+		StateDrivenTool<PickWaterHeight>::Init(initData, scenarioEditor);
+
+		wxASSERT(initData);
+		m_Sidebar = static_cast<EnvironmentSidebar*>(initData);
+	}
+
+	void OnDisable()
+	{
+		if (m_Sidebar)
+			m_Sidebar->UpdateEnvironmentSettings();
+	}
+
+	struct sWaiting : public State
+	{
+		bool OnMouse(PickWaterHeight* WXUNUSED(obj), wxMouseEvent& evt)
+		{
+			if (evt.LeftDown())
+			{
+				POST_COMMAND(PickWaterHeight, (evt.GetPosition()));
+				return true;
+			}
+			return false;
+		}
+	}
+	Waiting;
+};
+
+IMPLEMENT_DYNAMIC_CLASS(PickWaterHeight, StateDrivenTool<PickWaterHeight>);
Index: ps/trunk/source/tools/atlas/GameInterface/Handlers/EnvironmentHandlers.cpp
===================================================================
--- ps/trunk/source/tools/atlas/GameInterface/Handlers/EnvironmentHandlers.cpp
+++ ps/trunk/source/tools/atlas/GameInterface/Handlers/EnvironmentHandlers.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2016 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -198,6 +198,43 @@
 };
 END_COMMAND(RecalculateWaterData)
 
+BEGIN_COMMAND(PickWaterHeight)
+{
+	entity_pos_t m_OldWaterHeight, m_NewWaterHeight;
+
+	void Do()
+	{
+		CmpPtr<ICmpWaterManager> cmpWaterManager(*g_Game->GetSimulation2(), SYSTEM_ENTITY);
+		ENSURE(cmpWaterManager);
+
+		CVector3D worldPos = msg->screenPos->GetWorldSpace();
+		m_OldWaterHeight = cmpWaterManager->GetWaterLevel(
+			entity_pos_t::FromFloat(worldPos.X), entity_pos_t::FromFloat(worldPos.Z));
+		m_NewWaterHeight = entity_pos_t::FromFloat(worldPos.Y);
+		SetWaterHeight(m_NewWaterHeight);
+	}
+
+	void Redo()
+	{
+		SetWaterHeight(m_NewWaterHeight);
+	}
+
+	void Undo()
+	{
+		SetWaterHeight(m_OldWaterHeight);
+	}
+
+	void SetWaterHeight(entity_pos_t height)
+	{
+		CmpPtr<ICmpWaterManager> cmpWaterManager(*g_Game->GetSimulation2(), SYSTEM_ENTITY);
+		ENSURE(cmpWaterManager);
+
+		cmpWaterManager->SetWaterLevel(height);
+		cmpWaterManager->RecomputeWaterData();
+	}
+};
+END_COMMAND(PickWaterHeight)
+
 
 QUERYHANDLER(GetEnvironmentSettings)
 {
Index: ps/trunk/source/tools/atlas/GameInterface/Messages.h
===================================================================
--- ps/trunk/source/tools/atlas/GameInterface/Messages.h
+++ ps/trunk/source/tools/atlas/GameInterface/Messages.h
@@ -503,7 +503,9 @@
 		((sEnvironmentSettings, settings))
 		);
 
-COMMAND(RecalculateWaterData, NOMERGE, ((float,unused)));
+COMMAND(RecalculateWaterData, NOMERGE, ((float, unused)));
+
+COMMAND(PickWaterHeight, NOMERGE, ((Position, screenPos)));
 
 QUERY(GetSkySets,
 	  // no inputs