why thank you, Mike, for all that seemingly complete research done on my behalf! Coastal Border List having been done so fast, I suppose I will now move on to internal waters - lakes, rivers and the like.
Since shore boundarues are a little more common than coastal, I shall stay with international borders only. But there's also a rather interesting situation that I found in Lithuania.Now, I've seen a few lakeshore municipality boundaries, but this is in the Curonian Lagoon. Map attached does the explaining.