Can anyone tell me why I'm getting all these black lines around the shorelines?  I don't quite think I'm getting all I can out of this...

Kevin, looks to me as though they've edited the local LWM (Land Water Mask) to change the coastlines and haven't done a very good job.

If you've installed everything they've provided and it's above any mesh you have installed not much you can do. It's likely that their LWM/VTP bgls are separate in your new scenery folder. If they're identifiable, might be worth knocking them out and seeing what the effect is.

Also, have you got any mesh installed for this area that may be incompatible with this scenery ie this scenery might only work with default mesh