Hey @DanielOliveira,
Would this different approach fit your needs a little bit better?
First I created a cutting plane in the mid section to give me a clear vision of the water level; then I created a 2D plot to analyze alpha phase 1 [node]. Then simply click on nodes of interest (I could only select those in the walls).
Is there a better way to do this in paraview? Maybe a plot over line? @DaleKramer