With land in sight for the first time in nearly eight hours, an exhausted Summer and Cayci Underwood made a decision they hoped would save their lives -- they let go of their paddleboard.
The half-sisters, ages 21 and 27 respectively, let the current in the Calibogue Sound carry away what had been their life buoy.
Sunburned, scraped and exhausted, they swam for shore and, after 45 minutes in tough surf, collapsed on the sand of Hilton Head Island's South Beach, nearly 8 miles from their launch point on Tybee Island, Ga. It was just after 9:40 p.m.
"As soon as we got there, we just kind of fell down," Summer Underwood said Wednesday.
Beachgoers -- drawn by the pair's screams -- met them at the shore, helped them from the water and told them where they were -- Hilton Head Island.
It was a question they had been asking themselves since a storm struck earlier in the day and carried them so far from land that the tree line disappeared.
The sisters were shocked.
They were supposed to be on Tybee. That's where they'd launched twin paddleboards at 12:30 p.m.
"I think they thought we made it all up," Summer said. "Their faces were priceless."
The Underwoods, visiting Tybee from Athens, Tenn., were "lucky to be alive," according to a report by the Tybee Island Police Department, who had joined the U.S. Coast Guard, Chatham County Rescue and the Savannah Metropolitan Search and Rescue in trying to find them.
The sisters' first paddleboarding experience began calmly.
They launched from the Tybee Island Marina, paddled past the Cockspur Island Lighthouse and were heading toward a sandbar to take a break when the wind picked up and the choppy water began rocking their boards, occasionally knocking the two into the water. Both were wearing life jackets.
"It took us away so fast, there was no getting back from it," Summer said.
The sisters lost each other. They were cold and battered and briefly alone.
They found each other again when the storm passed and the sky cleared.
But the struggle to stay on their boards continued and left their legs scraped, according to reports from the Tybee Police Department and the Beaufort County Sheriff's Office. The sun badly burned both women.
As the Underwoods drifted, several boats passed but their screams for help were unheard over the sound of the motors, Summer said. Worried they would lose each other again, the pair let one board go and paddled together.
When they finally spotted land again about 7 p.m., the current was still working against them.
Summer said she was at first terrified to strike out in the open water unbuoyed.
"I thought, 'If we leave the board, we have nothing to hold onto if we don't make it to shore,'" Summer said. "It's sink or swim."
Once on the beach, EMS treated the sisters for shock and exhaustion and wrapped their injuries. They declined to go to a hospital, so officers brought them to their Tybee Island hotel.
Summer said the experience brought her closer to Cayci, who joined her on vacation by chance after Summer's plans to go with a friend fell through.
"I think they were an inspiration to each other," Summer's mother, 48-year-old Pauletta Gound, said in a telephone interview Wednesday from her home in Tennessee. "It was meant to be, we just didn't know what the reason was, I guess."
Gound said she "thanked God" the pair was safe.
She said she didn't know they were missing until they were ashore.
"I don't know how I would have reacted if they told me she was lost at sea," Gound said of her daughter.
On Wednesday, the bruised pair began another eight-hour journey -- the drive home to Athens, where their parents were waiting.
"I told (Summer), 'Well, at least you had a good vacation until the last day," Gound said.
"And it's going to be a good time tonight when she gets home."
Follow reporter Rebecca Lurye on Twitter at twitter.com/IPBG_Rebecca.