I worked out you can remove the surface plot by setting the opacity to 0. This isn’t quite good enough though, as I can’t work out how to only show the projection trace lines 
I just want the z axis projections showing, so I can plot a 3D scatter plot over the top of contour plot. The goal would then be to show the coordinates and depth values, when I mouse over a 3D scatter point.
Any suggestions would be awesome! Thanks in advance!