I "think" I may have found a solution. After "plotting" the shore line, I went to the closest "point" on shore, next to the island. I then stuck a new point on the island. The plotting process is similar to imagining a large rubber band, and each point is a pin, that "stretches" the rubber band, to form a polygon. I was able to form a polygon around each island, and "scooch" two points on the island, with two points on the shore, so it "appears" a single line connects the shore with the island. It makes sense, because you are plotting the water level, so the connecting line "should" disappear, as it is at the same level as the shoreline on both the island and main land.