By Erik Osking

“My regulator just about dropped out of my mouth,” Al Barefoot recalled. “I thought, what in the heck have we discovered here?” Just moments before, he had swum head first down a restrictive chimney that punctuated a depression in the sea floor at 180fsw. Following several strands of encrusted monofilament fishing line; Al worked his way deeper and deeper into the cave. Thousands of years of silt and crumbly rock fragments, disturbed by the upward flight of his regulator’s exhaust bubbles, clouded the water and streamed down around him. A few moments later, the passage became horizontal, and he found himself hovering above a rock balcony at 240fsw, overlooking a large subterranean chamber. Even though the room was full of clear water, his light could not illuminate either the bottom or the distant side. “It was obvious from the lack of a guideline, and the undisturbed nature of the passage, that no one had been down here before. I took a long last look, and then I swam back up the chimney through the silt cloud toward daylight. I couldn’t wait to tell the rest of the group what I had seen”.

The excitement that was that moment of discovery, finding a cave system that had yet to be described, did not come easily. Al Barefoot has been cave diving as long as just about anyone. For the better part of the last twenty years, Al has explored known submerged cave passage up and down the Florida peninsula, the Bahamas and Mexico. Along the way, he has chased many leads with the promise of new discoveries to eventual dead ends. This time, the outcome was entirely different.

Cave diving is one of the most, if not the most, gear intensive sports known to man. Logistically, preparing a group of cave divers to explore the depths offshore is a task of mammoth proportions. Long hours of gear preparation, gas blending, assembling back gas, deco and stage bottles, and checking and then rechecking equipment finally gives way to the back breaking hassle that is loading the boat. Deep cave diving offshore of the west coast of Florida begins hours before sunrise and ends with the sun setting in our boat’s wake.

Our days are long, not only because of gear preparation but also because of the distance that boat must travel to reach depths of any significance. The continental shelf off Sarasota, Florida has a very low gradient. One hundred miles due west and the depth to the sea floor is just 300fsw. Although, at first glance, this seems to be a hindrance, it is also a blessing. First, when the weather cooperates and you can get out to distant dive sites, you are one of the few that will go through the bother of a long boat ride to get there. Dive sites far offshore are abundant in marine life and notably absent of man’s influence.

Second, and most important regarding future discoveries, the expansive carbonate rock sea floor off the west coast of Florida undoubtedly holds many more treasures waiting to be discovered, like Diamond Rock Cave. During the Ice Ages (1.8 million years ago until 10,000 years ago), sea level was anything but static. Shorelines moved up and down the continental shelf, allowing vast areas of previously submerged carbonate rock to be subject to weathering and the development of sinks, springs, cave systems and other karst landforms. At the end of the Ice Ages, the ancient shoreline was located where we now have a depth of 300fsw. Since that time, sea level has been marching steadily higher to its present location. If you look at a bathymetric chart of Florida and locate the 300fsw isobath, you note Florida was roughly three times its current size 10,000 years ago. The vast majority of that extra land mass is now submerged off the west coast of Florida.

Now enters modern man and his rapidly changing technology. In a world full of “modern” sports, cave diving is still in its infancy. Gear and gear configurations constantly evolve, and techniques once thought to be some sort of ancient voodoo ritual become accepted practices. Although difficult to believe, only in the last decade has Nitrox become mainstream. The increase in the number of divers breathing Trimix, to depths previously considered risky breathing air, promises to open vast areas of the continental shelf off the west coast of Florida to exploration.

On this trip, the weather was definitely on our side. Our boat ride offshore, approximately 60 miles west of Sarasota, Florida, had been in absolutely flat seas. For most of the day, it was hard to tell where the Gulf of Mexico ended and the sky began. The horizon had a mirror-like quality to it. It’s hard to complain about calm seas. But in the absence of even the slightest breeze, gearing up into our doubles and exposure suits, midday, in September in southwest Florida, was unbearably hot.

The discovery of Diamond Rock Cave came on our second and last dive of the day. Just a few hours earlier, three of us dove to depths in excess of 300fsw at a nearby drowned sinkhole known as the “Green Banana”. Visibility was excellent - the bare rock walls of the Green Banana were covered with yellow and orange encrusting growth interspersed with the occasional coral polyp or sea urchin. Even the time spent during deco was interesting. Dozens of different types of jellyfish floated past in the current, some with bioluminescence. Al Barefoot had wisely deferred his deep dive of the day, just in case the GPS coordinates he had been given to check out by a local commercial fisherman hit pay dirt.

Our next dive site was thought to be a drowned spring due to the fact that pelagic fish species are known to congregate there during the winter months. The theory is that these open ocean fish are attracted by the relatively warm groundwater discharging into the much colder surrounding Gulf water. Groundwater flowing into the Gulf would indicate a drowned spring, and as such, held the remote possibility of offering unexplored cave passage. Few things in the life of a cave diver can compare with the opportunity to dive where no one has been before.

Pulling hand over fist down the anchor line against a slight current, Al and I began our drop toward a small sandy depression in an otherwise flat, featureless, Gulf sea floor. Beneath the surface, the visibility was over 100 feet, as it often is this far from terrestrial input. We could see the structure we came to investigate several minutes in advance of our arrival at depth. As we passed through the thermocline, dropping the nauseatingly warm 84F surface waters to a cooler 78F at 80fsw, a school of large Amberjack swam up from the bottom to greet us. Rushing toward us they darted here and there, bumping into the anchor line, like a pack of puppies looking for approval, but staying just out of reach.

Continuing our descent, we reached the sea floor at 165fsw, swam over a small rock ledge, then into the middle of the depression at a depth of 180fsw. At its center, a large, angular rock almost completely covered what appeared to be a solution shaft about 10 feet in diameter. Having already done my deep dive of the day just a few hours earlier, I could only look on in envy as Al descended head first into the restricted opening.

Al was disappearing into the cave system as two more divers from our party, Eric Reintsema and Chuck Gulick, swam toward the depression and began to inspect the rock-occluded opening. I decided to explore a little of the surrounding sea floor and found several more drowned karst features about 100 feet to the west of the main depression- a small cavern with two solution shafts in its floor at about 180fsw. One of the shafts dead-ended at 200fsw, but the other took a hard turn back toward the east. The small cave appeared to be scoured by fish activity, current, or both, quite possibly leading back to the original cave entrance. My bottom time being just about up, I headed back to the cave entrance. There I met up with the three other divers and we began the lengthy decompression stage of our return to the surface. Even during deco, you could tell that Al would have quite a story to tell once we assembled topside.

Summary

Since that first dive, we have collected additional data about the system now known as Diamond Rock Cave. The large room is 50 feet wide, has a ceiling at 230fsw (with a large fissure in it), and has a slight hourglass shape with its narrowest point at 300fsw. There is a slight hydrogen sulfide layer at 330fsw and the highest point of the debris mound is at 360fsw. Mainline has been extended to 390fsw. The rock walls are covered with an orange and yellow encrusting growth, similar to what we observed at the Green Banana. The presence of this growth, and the slight variance in visibility inside the system from dive to dive, suggests tidal pumping of some sort. From observations of fish life and physical characteristics of the system, it is thought that there are at least two entrances into the large room.

Due to the vast areal extent of the carbonate rock that composes the west Florida continental shelf, and the increase in the popularity of Trimix as a breathing gas, it is likely that many new cave systems will be discovered offshore.