diff --git a/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.C b/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.C
index 70e56a95d1..93277dbaa3 100644
--- a/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.C
+++ b/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.C
@@ -26,13 +26,14 @@ License
 \*----------------------------------------------------------------------------*/
 
 #include "writeFreeSurface.H"
-#include "addToRunTimeSelectionTable.H"
-#include "IOmanip.H"
 #include "interfaceTrackingFvMesh.H"
+#include "addToRunTimeSelectionTable.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
 namespace Foam
+{
+namespace functionObjects
 {
     defineTypeNameAndDebug(writeFreeSurface, 0);
 
@@ -43,72 +44,62 @@ namespace Foam
         dictionary
     );
 }
+}
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-bool Foam::writeFreeSurface::writeData()
+void Foam::functionObjects::writeFreeSurface::writeData()
 {
-    if (time_.writeTime())
+    // refCast<interfaceTrackingFvMesh>
+    auto* itm =
+        const_cast<interfaceTrackingFvMesh*>
+        (
+            isA<interfaceTrackingFvMesh>(mesh_)
+        );
+
+    if (!itm)
     {
-        const fvMesh& mesh =
-            time_.lookupObject<fvMesh>(polyMesh::defaultRegion);
-
-        interfaceTrackingFvMesh& itm =
-            refCast<interfaceTrackingFvMesh>
-            (
-                const_cast<dynamicFvMesh&>
-                (
-                    mesh.lookupObject<dynamicFvMesh>("fvSolution")
-                )
-            );
-
-        itm.writeVTKControlPoints();
+        // FatalError
+    }
+    else
+    {
+        itm->writeVTKControlPoints();
     }
-
-    return true;
 }
 
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-Foam::writeFreeSurface::writeFreeSurface
+Foam::functionObjects::writeFreeSurface::writeFreeSurface
 (
     const word& name,
     const Time& runTime,
     const dictionary& dict
 )
 :
-    functionObject(name),
-    name_(name),
-    time_(runTime),
-    regionName_(polyMesh::defaultRegion)
+    fvMeshFunctionObject(name, runTime, dict)
 {
     Info<< "Creating " << this->name() << " function object." << endl;
-
-    dict.readIfPresent("region", regionName_);
 }
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-bool Foam::writeFreeSurface::start()
+bool Foam::functionObjects::writeFreeSurface::execute()
 {
-    return writeData();
-}
-
-
-bool Foam::writeFreeSurface::execute()
-{
-    return writeData();
-}
-
-
-bool Foam::writeFreeSurface::read(const dictionary& dict)
-{
-    dict.readIfPresent("region", regionName_);
+    if (time_.writeTime())
+    {
+        writeData();
+    }
 
     return true;
 }
 
 
+bool Foam::functionObjects::writeFreeSurface::write()
+{
+    return true;
+}
+
+
 // ************************************************************************* //
diff --git a/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.H b/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.H
index 48d6d6a0fb..2c7dd593c8 100644
--- a/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.H
+++ b/src/dynamicFaMesh/interfaceTrackingFvMesh/functionObjects/writeFreeSurface/writeFreeSurface.H
@@ -24,7 +24,7 @@ License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
 Class
-    Foam::writeFreeSurface
+    Foam::functionObjects::writeFreeSurface
 
 Description
     A function object to write the control points on the free surface
@@ -34,18 +34,17 @@ SourceFiles
 
 \*---------------------------------------------------------------------------*/
 
-#ifndef writeFreeSurface_H
-#define writeFreeSurface_H
+#ifndef Foam_functionObjects_writeFreeSurface_H
+#define Foam_functionObjects_writeFreeSurface_H
 
-#include "functionObject.H"
-#include "dictionary.H"
-#include "fvMesh.H"
-#include "OFstream.H"
+#include "fvMeshFunctionObject.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 namespace Foam
 {
+namespace functionObjects
+{
 
 /*---------------------------------------------------------------------------*\
                         Class writeFreeSurface Declaration
@@ -53,30 +52,13 @@ namespace Foam
 
 class writeFreeSurface
 :
-    public functionObject
+    public functionObjects::fvMeshFunctionObject
 {
-    // Private Data
-
-        //- Name
-        const word name_;
-
-        //- Reference to main object registry
-        const Time& time_;
-
-        //- Region name
-        word regionName_;
-
-
     // Private Member Functions
 
-        //- Write data
-        bool writeData();
+        //- Write data unconditionally
+        void writeData();
 
-        //- No copy construct
-        writeFreeSurface(const writeFreeSurface&) = delete;
-
-        //- No copy assignment
-        void operator=(const writeFreeSurface&) = delete;
 
 public:
 
@@ -86,7 +68,7 @@ public:
 
     // Constructors
 
-        //- Construct from components
+        //- Construct from Time and dictionary
         writeFreeSurface
         (
             const word& name,
@@ -95,27 +77,30 @@ public:
         );
 
 
+        //- No copy construct
+        writeFreeSurface(const writeFreeSurface&) = delete;
+
+        //- No copy assignment
+        void operator=(const writeFreeSurface&) = delete;
+
+
+    //- Destructor
+    virtual ~writeFreeSurface() = default;
+
+
     // Member Functions
 
-        //- start is called at the start of the time-loop
-        virtual bool start();
-
-        //- execute is called at each ++ or += of the time-loop
+        //- Called at each ++ or += of the time-loop
         virtual bool execute();
 
-        //- Read and set the function object if its data has changed
-        virtual bool read(const dictionary& dict);
-
         //- No-op
-        virtual bool write()
-        {
-            return true;
-        }
+        virtual bool write();
 };
 
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
+} // End namespace functionObjects
 } // End namespace Foam
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
diff --git a/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfacePressure/freeSurfacePressureFvPatchScalarField.C b/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfacePressure/freeSurfacePressureFvPatchScalarField.C
index 727ffac8db..a659bcf4c9 100644
--- a/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfacePressure/freeSurfacePressureFvPatchScalarField.C
+++ b/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfacePressure/freeSurfacePressureFvPatchScalarField.C
@@ -137,21 +137,24 @@ void Foam::freeSurfacePressureFvPatchScalarField::updateCoeffs()
         return;
     }
 
-    const fvMesh& mesh = patch().boundaryMesh().mesh();
-
-    interfaceTrackingFvMesh& itm =
-        refCast<interfaceTrackingFvMesh>
+    // refCast<interfaceTrackingFvMesh>
+    auto* itm =
+        const_cast<interfaceTrackingFvMesh*>
         (
-            const_cast<dynamicFvMesh&>
-            (
-                mesh.lookupObject<dynamicFvMesh>("fvSolution")
-            )
+            isA<interfaceTrackingFvMesh>(patch().boundaryMesh().mesh())
         );
 
-    operator==
-    (
-        pa_ + itm.freeSurfacePressureJump()
-    );
+    if (!itm)
+    {
+        // FatalError
+    }
+    else
+    {
+        operator==
+        (
+            pa_ + itm->freeSurfacePressureJump()
+        );
+    }
 
     fixedValueFvPatchScalarField::updateCoeffs();
 }
diff --git a/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfaceVelocity/freeSurfaceVelocityFvPatchVectorField.C b/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfaceVelocity/freeSurfaceVelocityFvPatchVectorField.C
index 64a3d3136a..dcf18c7e79 100644
--- a/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfaceVelocity/freeSurfaceVelocityFvPatchVectorField.C
+++ b/src/dynamicFaMesh/interfaceTrackingFvMesh/fvPatchFields/freeSurfaceVelocity/freeSurfaceVelocityFvPatchVectorField.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2019 Zeljko Tukovic, FSB Zagreb.
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -95,18 +95,21 @@ void Foam::freeSurfaceVelocityFvPatchVectorField::updateCoeffs()
         return;
     }
 
-    const fvMesh& mesh = patch().boundaryMesh().mesh();
-
-    interfaceTrackingFvMesh& itm =
-        refCast<interfaceTrackingFvMesh>
+    // refCast<interfaceTrackingFvMesh>
+    auto* itm =
+        const_cast<interfaceTrackingFvMesh*>
         (
-            const_cast<dynamicFvMesh&>
-            (
-                mesh.lookupObject<dynamicFvMesh>("fvSolution")
-            )
+            isA<interfaceTrackingFvMesh>(patch().boundaryMesh().mesh())
         );
 
-    gradient() = itm.freeSurfaceSnGradU();
+    if (!itm)
+    {
+        // FatalError
+    }
+    else
+    {
+        gradient() = itm->freeSurfaceSnGradU();
+    }
 
     fixedGradientFvPatchVectorField::updateCoeffs();
 }