The team, which has been working on the device since 2013, launched a crowdfunding campaign in March on Indiegogo and raised nearly $900,000 to bring the product to market.

The developers of Triton claim their device would allow a user to breathe under water for 45 minutes at a maximum depth of 15 feet.

A crowdfunding campaign for a device allowing divers to breathe underwater without scuba gear has come under heavy scrutiny and refunded all of its campaign backers.

The device uses "artificial gills", a filter with holes smaller than water molecules but large enough for oxygen to pass through.

However, several articles have been published which are skeptical about whether the device would actually work. Writing for Deep Sea News in 2014, Dr. Alistair Dove, director of research and conservation at Georgia Aquarium, estimated that the device would need to filter 90 litres of water a minute to provide enough oxygen for the user.

Following several inquiries about the device and articles questioning whether the device worked as claimed, the company relaunched the campaign at the end of last week and refunded all their supporters.

In an effort to increase transparency and clarify how the device worked, Triton's developers revealed the device requires a cylinder of 'liquid oxygen' to provide enough breathable oxygen for the user. The cylinder will need to regularly replaced.

"What makes Triton work with the artificial gills is liquid oxygen," Saeed Khademi, co-founder & CEO of Triton, told CNBC via email. "For us, the difficulty to make Triton work was how to connect these two technologies in Triton. This is the way Triton can produce enough oxygen for a human to breathe from."

Triton also posted a 12-minute video to Youtube showing a man sitting underwater using the device to further support their claims.

Despite this, many remain skeptical. Stephan Whelan, founder of online diving community DeeperBlue, has warned people against supporting the campaign.

"We have to warn anyone even briefly considering this crowdfunding campaign that they need to consider very, very carefully putting a single dollar to this product," he wrote on DeeperBlue's website. "There is no actual proof the tiny 'liquid oxygen cylinder' technology exists as they describe it."

Since relaunching the campaign, Triton has already attracted almost $300,000 at the time of writing. Triton plans to ship the product to crowdfunding supporters by December 2016. When released to consumers it will retail at $399.