Background image moving vb.net - vb.net

Question

I'm trying to create a small game, but I'm getting trouble.
I would like the background image to move as a loop when the player is moving across the map. The following code is a sample of what I want but the reverse.
Public Class Form1
Private WithEvents Tmr As New Timer With {.Interval = 40}
Private water As New Bitmap("C:\TestFolder\Water.png")
Private waterposition As Integer = 0
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
PictureBox1.Size = New Size(240, 74)
Tmr.Start()
End Sub
Private Sub Tmr_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Tmr.Tick
waterposition += 1
If waterposition = water.Width Then waterposition = 0
PictureBox1.Invalidate()
End Sub
Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
e.Graphics.DrawImage(water, waterposition, 0)
If waterposition > 0 Then e.Graphics.DrawImage(water, 0 - (water.Width - waterposition), 0)
End Sub End class
And now, when I'm trying to reverse it (from right to left) The image won't redraw.
Private Sub Tmr_Tick(sender As Object, e As EventArgs) Handles Tmr.Tick
waterposition -= 1
If waterposition = 0 Then waterposition = water.Width
PictureBox1.Invalidate()
End Sub
Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
e.Graphics.DrawImage(water, waterposition, 0)
If waterposition < 0 Then e.Graphics.DrawImage(water, (water.Width + waterposition), 0)
End Sub
Any suggestion? Thanks