An experienced swimmer mysteriously drowned in a Georgia lake that some believe is haunted.

Terrell Shelton, 21, was swimming with his friends in Lake Lanier toward an island off of Robinson Park at around 2.40pm on Saturday when he went underwater and failed to resurface, the Hall County Sheriff's Office said.

Somebody nearby then tried to help Shelton, but was unable to reach him in time, according to 11Alive. 

Sheriff's deputies, Hall County Fire Rescue personnel and officers with the Georgia Department of Natural Resources responded.

Marine units, rescue boats and dive teams then scoured an area of roughly 30 feet-deep water where Shelton was last seen until around 9pm, when crews suspended the search due to the darkness.

Shelton's body was later recovered in about 14 feet of water after authorities used a remotely operated vehicle to continue the search at around 11.30pm.

His sudden death shocked his sister, Calista Shelton.

'Honestly I was shaking, I was freaking out,' she told WSB-TV. 'My brother is a good swimmer. How could this happen?'

The massive lake has been rumored to be cursed or haunted, with online discussions frequently pointing to the area's history - including the remains of roads, structures and cemeteries that were flooded when the reservoir was created in the 1950s, according to CBS News.

Many posts also reference Oscarville, a predominantly black community whose residents were expelled from Forsyth County in 1912 before the land was submerged beneath the lake decades later.

Officials, though, say there is a simple explanation for why authorities are regularly called to boating accidents, drownings and water rescues - the millions of people that visit it each year.

They say the underwater debris, sudden drop-offs, low visibility and heavy recreational traffic on the lake create dangerous conditions for both swimmers and boaters alike. 

'We always encourage people, if they're gonna be out, to wear a life jacket,' Department of Natural Resources Law Enforcement Division Corporal Kevin Goss told 11Alive.

'It's a very different lake than a lot of people are used to,' he explained. 'It's got a lot of trees, elevation, a lot of wake, and so we always encourage bringing flotation and definitely a life jacket if you're not comfortable with swimming.'

Terrell's death marks the seventh drowning on Lake Lanier this season.  

On social media, Calista remembered Terrell as 'a son, a brother, a partner, a friend and someone who was deeply loved by so many people.

'The pain of losing him so suddenly is impossible to put into words,' she wrote Sunday morning.

Calista then addressed her brother directly.

'Terrell, I wish I had more time with you,' she said. 'I wish we could have one more conversation, one more laugh, one more memory. 

'You will always be my brother and I will carry you with me for the rest of my life.' 

The heartbroken sister went on to ask her Facebook friends to 'please keep our family, his boyfriend and everyone who loved him in your thoughts and prayers as we navigate this devastating loss.'

Calista also shared an online fundraiser she created to help the family pay for Terrell's funeral and memorial expenses.

'His kindness, laughter and presence brought so much joy to those around him and the void left behind is impossible to put into words,' reads the GoFundMe, which had raised more than $2,000 as of Tuesday evening.