Agree, Clutch - but looks like a bit more than Shoreline Exclude may be needed. For example, as you spotted, it looks like there's a bit of Land Class still showing through (trees etc.). Although this probably isn't the case, is it possible the mask that the OP's using isn't matched precisely with the base image? In addition to the shoreline exclude, have you used something like SBuilderX or SBuilder to exclude water polygons (looks like you have), add new water polygon, and made your land polygon a "hole" in it, then a new bgl file? You probably have but just wracking my empty brains for something that may cause the problem. Are any other areas of land class scenery showing through? The "hole" and it's outline have to match quite precisely the "shore" in the image otherwise, I think, you'll get oddities like this.