Trouble masking an object in B&W Photo - Lightroom Classic

I'm having trouble masking a dark island from a distance in a near grayscale picture.  

I have a video that came out terrible becasue of the clouds and lighting situation.  It's out the window of a plane taking off at a remote island.  After converting the video to PNGs and using the various landscape filters in ACR and Lightroom Classic, I was able to add color and turn them into something completely attractive.

For the final minute or two of the video, the plane is so far away from the island that ACR can't recognize the island as vegitation or mountains, however the island is much darker than the water and sky.  I tried using the Color Range and Luminance Range masks to isolate the island, however it keeps selecting more of the picture than I want.

Can someone recommend to me the best way to mask just the island?

Note - I'm using the "sync" feature to apply the masks across several thousand pictures.  Keep in mind the plane is moving so the position of the island moves slightly in each frame.  While the AI "Mountains, Vegitation, Water" masks recalculate and re-generate across eash frame, the "Object" mask is not doing as good of a job, since there are objects close to the edge of the island (a marina) that I want to leave in the water mask, but slowly move their way into the object mask as the marina moves, as the plane moves.

See attached sample original and screenshots of the Luminance and Color masks. 

Conclusion:  If I can mask out the island without using the object tool, I think I'd be OK.  I just can't figure out how to do that.