# surfaceNormal

> The outward-pointing surface normal of the fluid, in world space. Points away from the submerged side; shape points with a negative separation from the plane are submerged. Defaults to _up (a flat horizontal water surface). Must be non-zero; the engine normalises it internally so it does not need to be unit length.

## Definition

* **Type:** Property
* **Namespace:** [Unity.U2D.Physics](/engine/6000.6/script-reference/unity/u2d/physics.md)
* **Assembly:** UnityEngine.PhysicsCore2DModule

```csharp
public Vector2 surfaceNormal { readonly get; set; }
```