Decal problem

Hello,

I'am trying to recreate the bounce of water on the ceiling in HDRP and the best way, I thought, would be to make a decal projection. However, as you can see in the picture, there is a very harsh edge on the decal boundary.

Don't know if it matters, I made a decal shader with the voronoi effect, but how to make it fade away in the shade color to avoid that edge? If that is not possible, what are other possible solutions?

Thanks