diff --git a/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C b/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C
index 1656d3b67a..2d804a6513 100644
--- a/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C
+++ b/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C
@@ -212,10 +212,7 @@ void Foam::waveSurfacePressureFvPatchScalarField::updateCoeffs()
     const uniformDimensionedVectorField& g =
         db().lookupObject<uniformDimensionedVectorField>("g");
 
-    const uniformDimensionedScalarField& pRef =
-        this->db().template lookupObject<uniformDimensionedScalarField>("pRef");
-
-    operator==(pRef.value() - rhop*(g.value() & zetap));
+    operator==(- rhop * (g.value() & zetap));
 
     fixedValueFvPatchScalarField::updateCoeffs();
 }
diff --git a/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.H b/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.H
index 1e9e30dbb1..65e9c005a4 100644
--- a/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.H
+++ b/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.H
@@ -29,7 +29,7 @@ Description
     the hydrostatic pressure based on a given displacement:
 
         \f[
-            p_rgh = pref - \rho*g*\zeta
+            p_rgh = - \rho*g*\zeta
         \f]
 
     \vartable
@@ -64,6 +64,11 @@ Usage
     The density field is only required if the flux is mass-based as opposed to
     volumetric-based.
 
+    It is possible to set the ambient pressure by specifying a pRef object in
+    the constant folder. The patch field with this boundary condition must be
+    oriented perpendicular to gravity and should be in the same plane as the
+    origin of the coordinate system.
+    
 See also
     Foam::fixedValueFvPatchField