Stanley Riggs remembers well when North Carolina’s legislature proposed making sea level rise illegal.

It was never seriously considered, in part because Stephen Colbert led a viral charge that made the idea a national joke, said Riggs, a former distinguished professor of geology at East Carolina University. He resigned last year from the North Carolina Coastal Resources Commission’s science panel, which he had co-founded and which worked on a controversial report on sea-level rise.

The controversy swirled around whether the report could include long-term predictions about sea levels, which the government (conservatively) said are “very likely” to rise 4.3 feet and could rise by 8 feet or more during this century.

In North Carolina, 53,238 homes would likely succumb to flooding if sea levels rose at roughly the midpoint of 6 feet, according to Zillow’s latest analysis. Nationwide, we found that 1.9 million homes worth a cumulative $916 billion could be underwater if seas rise 6 feet. (To be clear, sea levels are not expected to rise uniformly, but we chose a midpoint rather than differentiating sea level predictions for different coastal areas.)

Some 39 percent of homes projected to be underwater are valued in the top third of homes for their metro areas, according to our analysis. High-end places like Miami Beach and lower Manhattan are sinking millions of dollars into protecting themselves.

“The silver lining is that if top-tier markets mobilize and start to protect themselves, that will mean more and more businesses doing coastal protection work and flood resilience work, and hopefully as the market matures, prices [for protecting individual homes and whole communities] will come down, which could benefit lower-tier housing over time,” said Benjamin Strauss, Vice President for Sea Level and Climate Impacts at Climate Central.

The less rosy part of that picture are places like Greenville, N.C., which Riggs calls home. Although it is inland, when the nearby Tar River floods, he can be locked in for weeks. Ultimately, he said, people living in vulnerable coastal areas will “have to move, unless you grow gills.”

Parts of North Carolina are preparing. Coastal Swan Quarter, N.C., recently constructed an 18-mile-long dike for protection. It had been discussed since the 1940s, but debates ended after Hurricane Isabel in 2003 flooded nearly every home in town. About 25 of the town’s 300 residents sold their homes and left, The Virginian-Pilot reported.

Parts of Atlantic City, N.J., are a different story. A shocking 73 percent of homes there are expected to be underwater if seas rise 6 feet.

While a seawall currently exists to protect downtown, and bolstered sand dunes are planned to protect oceanfront mansions, residents outside those areas are not so lucky. Climate Central found high tides in Atlantic City already reach more than a foot higher than they did a century ago, with sea level rise accelerating.

Residents along Atlantic City’s Arizona Avenue, not in a protected zone, have watched their home values deteriorate because of increased flooding.

“A lot of people will become financially trapped,” Strauss said. “If their homes start to lose value sharply because of increased flooding, they can’t move. So they have to live with the flooding, and that’s what people are doing on Arizona Avenue in Atlantic City.”

Flooding doesn’t happen every day, at least not yet.

“It’s a few times a year, then a month, then a couple times a week that you have to put on tall boots and wade through water to a car that’s parked a few blocks away because you don’t want to ruin your car,” he said.

“We don’t know how big that problem is. We found it already started in Atlantic City. [It was] the first place we looked.”