Allow water walking actors to find path over water surface

apps/openmw/mwmechanics/actorutil.cpp

@@ -23,4 +23,10 @@ namespace MWMechanics
         MWBase::World* world = MWBase::Environment::get().getWorld();
         return (actor.getClass().canSwim(actor) && world->isSwimming(actor)) || world->isFlying(actor);
     }
+
+    bool hasWaterWalking(const MWWorld::Ptr& actor)
+    {
+        const MWMechanics::MagicEffects& effects = actor.getClass().getCreatureStats(actor).getMagicEffects();
+        return effects.get(ESM::MagicEffect::WaterWalking).getMagnitude() > 0;
+    }
 }

apps/openmw/mwmechanics/actorutil.hpp

@@ -31,6 +31,7 @@ namespace MWMechanics
     MWWorld::Ptr getPlayer();
     bool isPlayerInCombat();
     bool canActorMoveByZAxis(const MWWorld::Ptr& actor);
+    bool hasWaterWalking(const MWWorld::Ptr& actor);
 
     template<class T>
     void setBaseAISetting(const std::string& id, MWMechanics::CreatureStats::AiSetting setting, int value)

apps/openmw/mwmechanics/aipackage.cpp

@@ -419,7 +419,8 @@ DetourNavigator::Flags MWMechanics::AiPackage::getNavigatorFlags(const MWWorld::
     if (actorClass.isPureWaterCreature(actor)
         || (getTypeId() != AiPackageTypeId::Wander
             && ((allowToFollowOverWaterSurface && getTypeId() == AiPackageTypeId::Follow)
-                || actorClass.canSwim(actor))))
+                || actorClass.canSwim(actor)
+                || hasWaterWalking(actor))))
         result |= DetourNavigator::Flag_swim;
 
     if (actorClass.canWalk(actor))