I have one up
here you might like.
As to converting them, I reckon it depends where your coastline finishes in terms of the SimCity squares. I had lots of trouble converting the one I just linked to, because one of the sides was sitting at the right place and one side wasn't. From memory, I needed about 1.5 SimCity squares between the road and the edge of the water. The water and land have to have a very gradual slope, I don't know how many times I applied the shallow edging tool.
I also used the cheat to enable God mode again after I entered city building mode, 'cos it was a a complete PITA going back and forth between landscaping and road building.
I would recommend you have a look at the spacing on the side of the island that is working for you, then try to match that where it is not working.
I have an island/peninsula
here too.