Still unaccounted for are Jonathan Francis, 30, and his daughter, Viola, 12.
As of Sunday night, U.S. Coast Guard Chief Petty Officer Gabriel Settel couldn't verify whether either is alive or dead.
"Our hearts go out to the family and friends," Settel said.
Erie County Sheriff Paul Sigsworth said someone saw both — each in their own kayak — in the water around 5 p.m. Saturday.
The boaters paddled somewhere between a 1-mile stretch spanning from the shoreline of their Crystal Rock neighborhood to the Edison Memorial Bridge.
But another 12 hours transpired before Jonathan's girlfriend, Sheila McClain, reported the two missing around 5 a.m. Sunday.
A widespread hunt launched shortly thereafter, involving U.S. Coast Guard boats zipping through Sandusky Bay and a helicopter hovering high above the water.
Local authorities also scoured shorelines in Erie County and Ottawa County in hopes of finding the two.
The only evidence of their whereabouts occurred around 9 a.m. Sunday when rescue crews located two empty kayaks, one blue and the other green, near Lightner Road on Port Clinton's south side.
Various authorities said neither one of the kayakers wore a lifejacket, based on interviews and witness reports.
"If you are going to go in the water, you have to have personal flotation devices with you," Ottawa County Sheriff Steve Levorchick said. "Especially if you are in a low-craft boat, like a kayak or canoe, make sure you put your lifejacket on."
Extreme gusts on Saturday afternoon could've contributed to either or both tipping over and spilling into the bay, Levorchick said.
"Those kayaks aren't made for windy conditions," Levorchick said.
The area where Jonathan and Viola paddled through is about 6 feet deep.
But Captain Patrick Thompson, a master mariner and military ship expert, worries the two experienced a severe case of hypothermia.
"It's not terribly deep out there but the water was at 39 degrees (Saturday)," Thompson said. "At 39 degrees, it would have been freezing. Hypothermia doesn't take long to set in."
On Sunday afternoon, as the official search continued, neighbors walked along Crystal Rock's shoreline in hopes of spotting Jonathan or Viola.
The shoreline's only about a quarter-mile journey from the pair's Linwood Avenue home, where nearly two dozen concerned friends and family members convened around 1 p.m. Sunday.
"They are two wonderful people," Viola's mother Ruth Brown said, wiping away tears trickling down her face.
The pair were often inseparable.
"They would go swimming together, hiking together and do just about anything together outdoors, just to be active," Jonathan's mother Gwen Gwinner said.
Brown told friends about how artistic the Margaretta Middle School student is. The stories then shifted to Viola's maturity, always exemplifying a perfect role model to her two little brothers and younger sister.
"Everything she does is perfect," Brown said.
Jonathan, who's only daughter is Viola, recently dedicated himself to writing an autobiography.
"He was going to school but just wanted to be home with his daughter," Gwinner said. "He was very smart. He was the type of person who was friendly with people and always a polite person."
If anyone has any information about the search, contact the:
• U.S. Coast Guard at 313-910-1055
• Erie County Sheriff's Office at 419-625-7951