By Mark Parrish, Big Blue Unlimited

Intrepid cave diving team John Garvin, Mark Parrish and James Hurley
are exploring the underwater cave systems found scattered throughout the Turks & Caicos Islands. One of the most impressive subterranean waterways found so far has been a Blue Hole in North Caicos known as Cottage Pond.

In October 2001, an attempt was made to reach the bottom of this alluring deep hole thought to be located somewhere underneath the neighbouring hill and in over 200 feet of water.

The team first explored Cottage Pond over two years ago. They immediately realised that this was no ordinary freshwater pond, but an enormous sinkhole that opened up 65 feet underwater into a black abyssal saltwater chamber below. To determine the size and extremities of this hole was going to require some dedicated planning and some serious skill.

Garvin and Parrish went to the freshwater springs of northern Florida in the winter of 1999 to learn the specialised techniques of cave diving. Garvin, an accomplished deep diving instructor, also taught Parrish the use of mixed gas techniques that are required to reach the extreme depths encountered in the pond. The Providenciales-based duo met up with Hurley in North Caicos that year and were delighted to find shared interests in cave diving and the desire to explore the allure of Cottage Pond. Hurley turned out to be a keen underwater cartographer and side mount diver, skills that were to prove invaluable over the coming months.

The team had since been steadily exploring deeper and deeper into the Cottage Pond hole. The top 30 feet of the pond consists of reddish-brown fresh water, which is stained by tannin from the lush plant life that surrounds the area. Between 30 and 50 feet, the freshwater and saltwater layers mix, producing a “halocline” that makes vision look like wearing strong prescription reading glasses. The water also smells and tastes of hydrogen sulphide or “rotten eggs.” It tarnishes dive equipment and plays havoc with ears. Visibility can be drastically reduced at this point, forcing the divers to hold their computers within inches of their masks to read the displays. (Often, over an hour of decompression is required in this zone and communication between the team is by touch alone.)

It is a relief to enter the clear salt water below. At a depth of 65 feet, the sides of the pond contract into an oval opening approximately 10 by 20 feet wide. It is at this point that the pond changes from being an unassuming, conical shaped pond into an enormous deep hole. No light passes through the upper layers and the water, although clear, is blacker than night.

At around 75 feet, three small side tunnels were discovered. They are pushed back on a sediment laden ledge and guarded by stalactites, cave drip formations that prove that the pond was once above water. In January, 2001, Hurley had a narrow escape while trying to determine where these tunnels led. Using steel tanks mounted on his sides and underneath his arms, Hurley tied off his line and ventured in. Squeezing past the stalactites and into an opening no more than two feet high and about the same wide, he was able to pull himself over the fine sediment and almost 100 feet into one of the passages. Upon realising that the tunnel was actually getting smaller, Hurley decided that it would be prudent to turn around. This was easier said than done. The only course of action was to bury himself half into the sediment and ease his tanks and body around inch by inch. The visibility quickly reduced to zero and in the confusion, he lost contact with his line and reel, his only lead out to the main chamber and the anxiously awaiting Garvin.

It is at this point in cave diving that the diver might assess the sanity of where he is. Panic can easily set in and the air supply is finite. The experienced Hurley kept his head. He took slow, deep breaths, relaxed and Mother Nature came to his rescue. Cottage Pond is tidal in that somewhere it links to the sea, and it appears that these side tunnels might just be that link. As Hurley looked up, the water was becoming clear. The tide was washing away the visibility-reducing sediment and he caught sight of his line. Taking a firm hold of it, he wriggled his way out into the main chamber and then ascended to a very welcome gulp of fresh air.

Deeper into the main chamber, the ceiling and sides of the cave peel away and the chamber becomes bigger and bigger. It stretches underneath the adjacent hill and is soon large enough to accommodate a good size house. At a depth of about 120 feet, a very impressive flowstone formation begins on the southern wall. It is 30 feet wide and over 40 feet tall with long finger-like projections hanging over the abyss. It is also white in stark contrast to the brown walls and is another cave formation that proves that this portion of the pond was also once above water. It has been named the “organ pipes.”

It is not until 180 feet underwater that the first signs of the bottom are encountered. It is a cold, smelly silt and continues to slope deeper and deeper into the blackness. Despite the clarity of the water and the large halogen flashlights that the divers carry, it is impossible to make out all the sides of the chamber at one time. In fact, it is difficult to determine whether one is simply in a large hole or has entered a vast underground tunnel. A large tree trunk was found at 200 feet and a branch at 228 feet. This became the point of greatest descent for over a year and the cause of much discussion and wonder. As it turned out, this was tantalisingly close to the bottom.

The problems of diving in such extreme conditions are plentiful. The overhead environment requires the use of cave diving techniques and the depth requires various complex blends of gas for the different portions of the dive. For the deep dive team, is it necessary to have a nitrox travel mix for descent, a set of trimix doubles for the deep portion of the dive and an oxygen-rich mixture to accelerate decompression near the surface. The water is also cold and at about 70 degrees Fahrenheit, the extended dive times require a dry suit. Lugging all this equipment around in the Turks & Caicos heat requires considerable effort and plenty of rehydration.

After a warm-up dive on October 8, 2001, it was planned to make a deep push the following day. The team met early at Big Blue headquarters in Leeward but things went badly from the outset. It was discovered that due to a leak, one of the sets of double tanks was not at the required pressure. Garvin, master blender, hastily set about recalculating the percentages of gas that were needed to replenish the tanks. It was not the calm, easy morning that he needed. Upon reaching North Caicos it was also discovered that a harness required to attach an Argon bottle for dry suit inflation had broken. A jury rig had to be made. Then at Cottage Pond as the team was readying themselves for the dive, the final straw broke–the emergency oxygen regulator was malfunctioning. Despite the effort, cost and eagerness to make the dive, Safety Officer Garvin called off the dive and it was agreed to put it off for another day. The team was disappointed but a valuable lesson had been learned.

They returned to Cottage Pond on October 11 determined to do it right. Garvin and Hurley rigged up for the deep dive. Parrish, with an injured leg and less experience at depth, was the support diver. The day went well and at 12:45 PM the divers entered the water. At 1:10 PM they slipped beneath the surface in the centre of the pond. Their descent was rapid. At a planned depth of 260 feet, the deep divers had 20 minutes to reach their target and to ascend again to the first decompression stop at 80 feet. This short bottom time still equated to 85 minutes of decompression so it was paramount that they kept to schedule. They stopped briefly to switch to their deep breathing mixes at 100 feet and to trade “OK” signals. They passed the Òorgan pipesÓ at 4 minutes and the 228 foot tie-off point after 7 minutes.

Everything was going according to plan. A minute later, they reached what appeared to be the bottom at 247 feet and they set about exploring their surroundings. Time was of the essence. They found the outside wall and followed the perimeter. After a further 6 minutes and reaching a maximum depth of 255 feet, they stopped to appreciate the enormity and beauty of where they were. Satisfied that they could go no further, they started their slow ascent to the surface and to the long decompression that awaited. Parrish met them eagerly at 100 feet to check that all was okay and to hear the news. He accompanied them through their decompression stops to monitor equipment and gas consumption.

At 255 feet underwater and using over 600 feet of line, they had reached their objective. There followed a great sense of achievement and jubilation at the climax of this two-year goal. What remains is the continued survey and mapping of Cottage Pond, the collection and identification of organisms that have been encountered and the study of life in this strange and wonderful environment. Who knows what exists and what secrets lie in the boundary between the fresh and salt water? Some say that these haloclines hold clues to the origins of life itself. And then of course there are the side tunnels. It is known that Cottage Pond leads to the sea and it seems likely that these tunnels are the link. Perhaps another day . . .

Many thanks to Ian White for his huge support of exploration in October. The team would also like to thank Holton Williams, Hormel Harvey, Big Blue Unlimited, O2 Technical, MediaWorks, the Extended Range Foundation and the offices of Twa, Cochrane and Skatfeld.

For more information on the Caicos Caves Project, visit www.caicoscavesproject.com.