CoolChef, I know building right on the wáter has many regulations, as you say. I get the impression that some of the rural inland municipalities, such as Tahmek, Yucatán, don`t have many rules. A friend who built there said it was merely considered a courtesy if one informed the municipality that they planned to build a house.
I don`t recall her having a single inspector from the municipality, just one from CFE.
By the way, thanks for bringing up this fascinating topic !