Windsurfer trails leaving permanent artifacts

[burningthumb]

I raised this issue on the boat attack project but I'll raise it here in more detail. I'm using the rendergraph-u6 branch and have two windsurfers as well. The windsurfers have a particle effect that leaves a trail. This trail appears to be permanently "burned" into the water and as the camera moves, the artifacts move with it.

If I frame on a surfer and follow it for a while, them zoom out you can really see how it looks on the water plane.

I know its the trails because if I disable them, everything works fine.