Multiple people were taken to hospitals, and crews from the US Coast Guard, the McIntosh County Fire Department, the Georgia Department of Natural Resources and others were searching the water for any other survivors, said Tyler Jones, a spokesman for the Georgia Department of Natural Resources.
Jones said a gangway at the dock collapsed and sent people plunging into the water.
It happened as crowds gathered on the island for a celebration of its tiny Gullah-Geechee community of Black slave descendants.
Sapleo Island is about 100km south of Savannah and is reachable from the mainland by boat.
Jones said he did not know what caused the gangway to collapse, but officials believe there were at least 20 people on it at the time. The gangway connected an outer dock where people board the ferry to another dock onshore.
Helicopters and boats with side-scanning sonar were used in the search, according to a Department of Natural Resources statement. The cause of the collapse is being investigated.
Among the dead was a chaplain for the Georgia Department of Natural Resources, Jones said.
Georgia Governor Brian Kemp said he and his family were "heartbroken by today's tragedy on Sapelo Island".
"As state and local first responders continue to work this active scene, we ask that all Georgians join us in praying for those lost, for those still in harm's way, and for their families," Kemp said on the social platform X.
Marty, the girls, and I are heartbroken by today's tragedy on Sapelo Island. As state and local first responders continue to work this active scene, we ask that all Georgians join us in praying for those lost, for those still in harm's way, and for their families.— Governor Brian P. Kemp (@GovKemp) October 19, 2024
The deadly collapse happened as island residents, family members and tourists gathered for Cultural Day, an annual fall event spotlighting the island's tiny community of Hogg Hummock, home to a few dozen black residents. The community of dirt roads and modest homes was founded by former slaves from the cotton plantation of Thomas Spalding.
Small communities descended from enslaved island populations in the South - known as Gullah, or Geechee in Georgia - are scattered along the coast from North Carolina to Florida.
Scholars say their separation from the mainland caused residents to retain much of their African heritage, from their unique dialect to skills and crafts such as cast-net fishing and weaving baskets.
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