Don't allow casting Water Walking in deep water

apps/openmw/mwbase/world.hpp

@@ -385,6 +385,7 @@ namespace MWBase
             ///Is the head of the creature underwater?
             virtual bool isSubmerged(const MWWorld::ConstPtr &object) const = 0;
             virtual bool isUnderwater(const MWWorld::CellStore* cell, const osg::Vec3f &pos) const = 0;
+            virtual bool isWaterWalkingCastableOnTarget(const MWWorld::ConstPtr &target) const = 0;
             virtual bool isOnGround(const MWWorld::Ptr &ptr) const = 0;
 
             virtual osg::Matrixf getActorHeadTransform(const MWWorld::ConstPtr& actor) const = 0;

apps/openmw/mwmechanics/spellcasting.cpp

@@ -383,6 +383,21 @@ namespace MWMechanics
             }
             else
                 canCastAnEffect = true;
+          
+            if (magicEffect->mIndex == ESM::MagicEffect::WaterWalking)
+            {
+                if (target.getClass().isPureWaterCreature(target))
+                    continue;
+
+                MWBase::World *world = MWBase::Environment::get().getWorld();
+
+                if (!world->isWaterWalkingCastableOnTarget(target))
+                {
+                    if (caster == getPlayer())
+                        MWBase::Environment::get().getWindowManager()->messageBox ("#{sMagicInvalidEffect}");
+                    continue;
+                }
+            }
 
             if (!checkEffectTarget(effectIt->mEffectID, target, castByPlayer))
                 continue;

apps/openmw/mwworld/worldimp.cpp

@@ -2077,6 +2077,19 @@ namespace MWWorld
         return pos.z() < cell->getWaterLevel();
     }
 
+    bool World::isWaterWalkingCastableOnTarget(const MWWorld::ConstPtr &target) const
+    {
+        const MWWorld::CellStore* cell = target.getCell();
+        if (!cell->getCell()->hasWater())
+            return true;
+
+        // Based on observations from the original engine, the depth
+        // limit at which water walking can still be cast on a target
+        // in water appears to be the same as what the highest swimmable
+        // z position would be with SwimHeightScale + 1.
+        return !isUnderwater(target, mSwimHeightScale + 1);
+    }
+
     bool World::isOnGround(const MWWorld::Ptr &ptr) const
     {
         return mPhysics->isOnGround(ptr);

apps/openmw/mwworld/worldimp.hpp

@@ -481,6 +481,7 @@ namespace MWWorld
             virtual bool isSwimming(const MWWorld::ConstPtr &object) const;
             virtual bool isUnderwater(const MWWorld::CellStore* cell, const osg::Vec3f &pos) const;
             virtual bool isWading(const MWWorld::ConstPtr &object) const;
+            virtual bool isWaterWalkingCastableOnTarget(const MWWorld::ConstPtr &target) const;
             virtual bool isOnGround(const MWWorld::Ptr &ptr) const;
 
             virtual osg::Matrixf getActorHeadTransform(const MWWorld::ConstPtr& actor) const;