There wasn’t supposed to be any water, let alone waves lapping U.S. 80 as Paul Wolff tooled back from Savannah on a spring evening five years ago. The Chevy Metro rolled down the eastern side of the Bull River bridge and smack-dab into an unnaturally high tide pushed leeward by strong southeasterly winds.

“The water was coming right over the marsh. It was scary,” said Wolff, a Tybee Island councilman. “I just plowed right through it.”

He learned two costly lessons that night. One, the car’s undercarriage had to be replaced. Two, high tides are dangerous, occur with greater frequency and will cost coastal Tybee Island tens of millions of dollars to prepare for.

U.S. 80 is the only road on and off Tybee Island and it floods, in spots, about a half-dozen times a year, usually during spring high, or “king,” tides. By 2060, according to Georgia scientists, the road is expected to flood 50 times a year due to climate change and its impact on sea levels.

Tybee, largely at the urging of Wolff, takes climate change more seriously than any other Georgia community. With good reason. Two-thirds of the island could be under water within a century if current predictions of sea-level rise prove true, according to the National Oceanic and Atmospheric Administration.

A tidal gauge just off Tybee’s western edge shows that the Atlantic Ocean here has risen, on average, an inch every decade since 1935. Since the 1990s, though, the degree of sea-level rise has tripled, says Clark Alexander, the director of the nearby Skidaway Institute of Oceanography.

An additional three feet of water, as projected, would submerge Tybee’s southwestern corner and hundreds of homes built there upon river bottom reclaimed in the 1930s for real estate development.

“Tybee,” Alexander said, “would be in a world of hurt.”

In 2012, the feds put up $100,000 for a Community Climate Adaptation Initiative to study the impact of sea-level rise on Tybee over the next 50 years. The report details the most endangered parts of the island and which infrastructure — roads, wells, storm water drains — should be climate-proofed.

A flooded U.S. 80 isn’t the only precursor of what’s in store for the island’s 3,000 year-round residents. High tides and heavy rains create ponds of water that too slowly disappear. Flooding is exacerbated by tidewater clogging the storm drains.

“We are facing imminent challenges from rising sea levels due to climate change,” said Wolff, 64, who runs a bed-and-breakfast, draws energy from rooftop solar panels and bikes everywhere on the island. “The good news is it’s coming slowly enough. We hope we’ll have time to adapt.”

The city is planning for a 14- to 20-inch sea-level rise by 2060. It has already mandated that new driveways be permeable to allow rainwater to seep into the ground. It is identifying properties at risk of flooding. It will study the financial feasibility of elevating houses out of the flood plain, which, eventually, could result in lower flood insurance premiums.

The city spent $60,000 on two tide gates to prevent seawater from clogging storm drains during heavy rains. A “living shoreline,” created with mud and oyster shells, will be built around the island’s southwestern edge. The electronics controlling Tybee’s three water wells will be flood-proofed at a cost of $200,000 each.

Federal and state treasuries covered most of a recent $11 million beach renourishment plan. State transportation officials are considering a $100 million upgrade to flood-proof U.S. 80.

“If we don’t want to be treading water or having our grandchildren growing gills, we definitely need to spend this money now instead of putting it off,” Wolff said as distant thunder presaged a storm. “The longer we procrastinate, the more expensive it will be.”