Published: Sep 27, 2013 12:31 PM EDT
Updated: Sep 29, 2013 2:24 PM EDT

LEE COUNTY, Fla. - The last thing you want to hear is that you have a sinkhole in your backyard. Well, guess what? We do! Fortunately, the sinkhole we're talking about is thirty miles off Lee County's shoreline in the Gulf of Mexico.

The mysterious Captiva Blue Hole beckons to be explored by advanced SCUBA divers like myself, News-Press partner Kevin Lollar and Richard Black, owner of Florida Dive Connection.

"Visibility is not more than 30 to 40 feet, so you can't really tell there's another side to it. You can just tell that it's a dark, deep hole," says Black.

A native of Florida, Black is at home as much underwater as he is on land. Describing himself as mostly a cave and technical diver, Black has explored almost every spring in Florida. Combine his love for cave diving and spring diving, and you find the perfect combination, the Captiva Blue Hole. "My first impression of the Blue Hole was that it looked just like a spring in north Florida, except there were no cypress trees and it was underwater," he says.

Ninety feet below the surface on an otherwise sandy bottom, the massive sinkhole is flourishing with life. I descend into the hole to a maximum depth of 105 feet and explore its walls, covered in soft corals and smaller aquarium-sized fish.

"There's a sense of the unknown, and if you're anything of an explorer you can't help but to feel excited and curious," says Black.

Unfortunately, invasive lionfish have also moved in and become a huge problem for the Gulf. The beautiful but venomous fish eat almost anything, and so far no one has discovered an underwater predator. We spear and kill 13 lionfish on our one dive alone.

Small fish, both good and bad, share the 185 foot deep hole with their much larger cousins, goliath grouper, amberjack and barracuda. Most of the sea-life thrives around the rim of the hole and 20 feet into the opening, a miniature reef system only in reverse.

"When you think of reefs, you think of rocks coming off the bottom and fish living on them. Well this is the opposite, the rocks go down into a hole," explains Jim Culter, Senior Scientist at Mote Marine Laboratory in Sarasota.

Culter has done more than 100 dives into blue holes, researching these sinkholes' sea-life and history. He has explored the Captiva Blue Hole to a depth of 165 feet and says that because of lack of circulation, marine-life becomes less abundant as one descends deeper into the hole .

"There's a lot to be learned about them in terms of their role in the ecosystem," says Culter.

So where do these underwater sinkholes come from? Culter explains, "Approximately eight to twelve thousand years ago, the sea level was much lower and the coastline of Florida was 100 miles farther west." And just like Florida today, sinkholes existed then, too, only above water. In time, the sinkholes have filled with water and created a unique habitat for fish and a playground for advanced divers.

Only two dive sites remain in our SCUBA series, and next month WINK News and our partners at the News-Press explore the ARC Towers, three obsolete cell phone towers that have transformed from a hub for communication into a home for numerous goliath grouper.