The huge narrow hole has fascinated researchers, who are preparing to venture inside it to discover which creatures it contains.
Named the “Green Banana”, the hole lies about nearly 50 metres beneath the surface of the sea and is thought to be among 20 on Florida's coastal continental shelf.
Experts from the National Oceanic and Atmospheric Administration (NOAA) have already collected 17 water samples from the area surrounding the hole along with four sediment samples.
They now plan to embark on a new mission to a second, deeper area of the hole in August, with scientists joining from Mote Marine Laboratory, Florida Atlantic University, Georgia Institute of Technology and the US Geological Society.
“They are basically old springs or old sinkholes that formed something like eight to ten thousand years ago,” Dr Emily Hall, of the Mote Marine Laboratory and Aquarium, told Fox 13.
“We don’t know whether it's connected to a cave system or if there’s ground water coming in or out.
“We have noticed that there are high levels of nutrients coming out of these holes, we know the carbonate chemistry is very different from the surrounding water which could be related to future climate changes, things like ocean acidification.”
NOAA said in a statement: "Little is known about blue holes due to their lack of accessibility and unknown distribution and abundance.
“The opening of a blue hole can be several hundred feet underwater, and for many holes, the opening is too small for an automated submersible."