Chilling photo shows moment two Oklahoma students almost died after taking sip of water at Cancun swim-up bar: Here's what they think happened to them

A terrifying photograph shows the moment two Oklahoma college students were potentially drugged at a swim-up bar in Cancun - with one of the young vacationers fearing she ingested fentanyl. 

Zara Hull, her boyfriend, Jake Sinder, and her friend, Kaylie Pitze, were with a group of friends in Cancun for a dream vacation when their trip turned into a nightmare on August 2.

'We both got water and within two minutes, Jake had turned around and we both hit the bar, heads down at the same time,' Hull, 20, told CBS News. 

Hull said she experienced convulsions before passing out and becoming 'basically paralyzed.'

Snider rushed her to the hospital and remained by her side as staff reportedly demanded thousands of dollars for treatment.

'They had increased the money they wanted. The baseline was $10,000 for them to even look at me,' Hull said. 

'They were holding me captive. We're college students; we don't have the money they're asking for.'

Meanwhile, she suffered from seizures throughout the night, and the doctors intubated her.

'The hospital was NOT treating her, they were pumping her full of so many drugs to keep her sedated,' Jake's mother, Stephanie Snider, wrote on Facebook.

'They intubated her and told Jake it was "sedation for the MRI," she continued. 'There was no reason to sedate her, let alone intubate her.'

'We knew we needed to get her back and to the US.'

But hospital staff demanded even more money to release her, and the air ambulance to bring Hull back to the United States cost $26,000. 

A day after ingesting the suspicious beverage, the group secured a private plane to fly them to Dallas, where Hull remains in the hospital as doctors continue to work to determine what may have happened to her. 

She initially could not breathe on her own and was put on a ventilator. 

Doctors say they have not found anything wrong with Hull, even though she has experienced at least 18 convulsions.

They say it is possible that the she was drugged. 

'We think it was possibly synthetic fentanyl,' Hull told KFOR. 

She will require physical therapy to learn how to walk again.

Kaylie did not end up in the hospital, but had a tough 24 hours after she was possibly drugged. 

'It's been three days now and she still doesn't feel back to herself,' Stephanie Snider said.

'Neither of the girls have any memory of what happened after they took that last drink, which happened to have been a glass of WATER.'

The college students have declined to reveal the names of their hotel or hospital, fearing for their safety. 

The families have started several GoFundMe pages to ask for help covering the students' medical costs. 

Since returning to the U.S., Hull has made some progress, her family said.

On Sunday, she was able to start breathing on her own and was taken off a ventilator, a family friend wrote in the online fundraiser for her medical expenses.

'She is awake and able to communicate with family and her health care team,' the update said.

Then on Monday night, her family friend said she was able to get out of bed, and with help she was able to walk to the bathroom.

Hull has since been moved out of the intensive care unit and is now in a neurology unit out of precaution.

Still, she says she is struggling - even as her friends came to visit her in the hospital.

'It's so scary because there's times I am like, 'Am I going to make it out of this?' she said.