Change polygon's edges based on another feature

I’m trying to map out fishing areas. I had a description of their western and eastern limits, and min/max operating distance from the shore, which I turned into a list of coordinates for their NW, NE, SW and SE corners. I then generated polygons shaped like parallelograms, which worked for the most part, because the coastline in my study area is usually in a straight line. However, there are some areas where it’s not the case and my polygons overlap with the coast, like so:

I also have other polygons that don’t overlap with the coastline, but don’t parallel it and therefore don’t represent the correct min/max operating distance from shore throughout their whole area.

I have a line feature of the coastline itself, and several buffer features that represent different distances from the coastline. Is there a solution where I can use these features to easily/automatically re-shape the polygons so that they are at the correct distance from shore throughout their whole area, not just at the corner vertices? This would have to identically modify both the top and bottom edge of the polygons so that they remain parallelograms.