Three years after Hurricane Sandy left the Jersey Shore in flood-soaked tatters, the debate over how to defend homes and businesses there against the next big storm rages on, pitting neighbor against neighbor and driving the state to sue owners of beachfront property.

The obvious answer, many flood-prevention experts and elected officials say, is to build huge dunes to hold off the surging tide. But even as crews bulldoze sand dredged from the floor of the Atlantic Ocean to form a bulwark along stretches of the shore, homeowners are still standing in the way of consensus.

The holdouts have driven the state to invoke its eminent domain over their land and angered Gov. Chris Christie enough that he urged residents of some towns to go “knock on doors” and confront the homeowners, who he said were being selfish. Some of those residents, in turn, have challenged the Christie administration to be more forceful in support of the dunes.

Through three summer seasons, the seemingly anodyne plan to have the federal government pay for the construction of protective dunes has caused division, frustration and fear among residents of shore towns.