Creating Heat Map using Filled Map - How to only include land boundary for county

Hello everyone, 

I am just diving into Power BI, creating my first heat map and not having luck with something that seems like it should be simple to correct.  In Michigan we are surrounded by Lakes and when building a county level map the county borders for those on a shoreline extend in the water. My guess is that the system is reporting it correctly as the county border extends to the "State line" which is in the middle of the lake but hoping there is a way to filter for land only or somehow not show the county extended into the water.  Thanks for any help or guidance.