Project Overview

The Great Blue Hole of Belize

Aqua Venture and divers

Survey of the gallery on the SW Wall

Matt takes a sample of a stalactite

One of the great destinations for divers interested in spectacular and rare underwater sites is the 1000 foot diameter "Great Blue Hole of Belize" located on Lighthouse Reef atoll in central America, just 50 miles from Belize City. This feature is similar to the famous cenotes found farther to the north in the Yucatan of Mexico. Yet, it is different. It lies completely submerged in sea water, and as we found, contains unique features, previously undescribed.


In 1970, Jacques Cousteau and his team aboard the Calypso explored the Blue Hole and dove to the bottom in two, one man submersibles to depths of 415 feet. Dr. Robert Dill directed Cousteau’s scientific operations and collected shallow samples (one was a stalactite from 90 feet that had fallen to a 160 foot ledge) from the Blue Hole. In 1995, Terrence Tysall, president of the Cambrian Foundation, led a six man team to Belize to become the first open circuit scuba divers to dive to the bottom. Five divers touched down on the bottom in the center and reached 408 feet.

In June 1997, Terrence put together another team, this time with more scientific objectives. This 1997 expedition, unlike the Cousteau and the later deep diving expedition, was scientifically oriented and utilized the new technologies provided by deep trimix diving to support sampling in areas not reachable by remotely operated vehicles or submersibles. The scientific efforts were once again led by Dr. Robert Dill, his first return to the Blue Hole in 27 years. He was assisted by another geologist, Dr. Anthony Jones, from Canada. Food, lodging (luxurious beach villas), tanks and compressor use for sixteen divers for two weeks was graciously provided by Lighthouse Reef Resort. All remaining sets of scuba and support equipment were contributed by expedition members.


The primary objective was to locate and retrieve speleothems (cave decorations) from the bottom to help establish a time line for the rising sea levels related to continental ice sheet melting following the last ice age, thus giving us a geological history of the western Caribbean.

There were several secondary objectives for the expedition. Sediment samples were taken from the bottom in an attempt to confirm a theory that periodic increases in iron levels in the water (coming from the unusually large dust storms that originate over the Sahara desert in Africa) act as fertilizers to marine plants. These stimulated growth periods increase the plant population and enable them to overgrow corals. In addition, these soils contain pathogens and fungi that are causing a degradation of coral reefs throughout the Caribbean.

Additionally, exploration for potential cave systems leading to or from the blue hole that could be related to periods of time when the rising sea stabilized, permitting cave formation.

The deep divers were using computer based, theoretical deep diving tables. Doppler samples were also taken on some of the deep divers by Dr. Andrew Pitkin, Deputy Director of Hyperbaric Medicine for the Royal Navy. Doppler sampling uses high resolution acoustic probes to monitor bubble formation in the blood stream. None of the deep teams developed any decompression sickness and three divers, Kyle Creamer, Terrence Tysall, and Andreas Matthes showed little indication of bubble formation, an indication that the theoretical tables are indeed valid and the methods of decompression used were preventing adverse reactions to the deep trimix diving.

Dr. Clyde Martin from Tennessee conducted bacteria sampling of regulators to determine if certain bacteria could become a problem in the presence of high partial pressures of oxygen. Cultures were collected to determine if certain bacteria, causing pneumonia like symptoms, would have an accelerated growth rate on the regulators used for the deep (greater than 230 feet) dives.

Swift Current Productions videoed all aspects of land preparations and exploratory scuba dives. A short segment will air on SeaTek on the Learning Channel and a documentary will be prepared for possible airing on other cable channels. And finally, the owners and manager of Lighthouse Reef Resort asked the team to explore a deep cave system in front of the resort they named "the Abyss." The location of this formation at the north end of the atoll made it a potentially interesting discovery because of the similarity to the Blue Hole.

Amazingly, all of these objectives were accomplished in 14 days.


Each team member had several duties depending on what they were trying to accomplish on any given day. Eight of the sixteen members had the training required to go to the bottom, however, even these divers acted as support divers, exploratory divers and shore support members throughout the expedition.

Shore support started the first day with oxygen cleaning and setting up the stage cylinders and a number of doubles using 28 of the aluminum 80s loaned to us by Lighthouse Reef Resort. The team also off loaded and set up the K cylinders of helium and oxygen, the booster pump and most of the diving equipment (including six sets of steel doubles), all of which were brought over from Belize City by boat. On a daily basis, the shore support team saw to it that the required stage cylinders and bottom cylinders were filled or mixed and ready for analysis for the next day’s diving.

The deep divers carried trimix in steel doubles (95s, 104s or 108s) on their backs and three 80 cubic foot aluminum stage cylinders. One stage was air, used for a travel mix and deep decompression stops. The second stage was enriched air nitrox (EAN40) for decompression stops between 100 and 30 feet. The third stage was pure oxygen used at 20 and 10 foot decompression stops. The second and third stages were sometimes carried but often staged on a ledge or descent line.

A 15 minute dive to 410 feet would require over two and a half hours in the water with decompression stops beginning at 160 feet. If the deep divers had reasonably good air consumption rates, they would consume a total of 261 cubic feet of the different gases. To follow the rule of thirds, each deep diver would be required to carry 7 stage cylinders. To prevent overloading the deep divers, we used safety divers with redundant stage systems (an extra cylinder and regulator), and these divers had the ability to return directly to the surface if it became necessary.

There was a deep support diver and a shallow support diver for each deep team. Both support divers carried air in their double aluminum 80s on their backs. The deep support diver carried one stage cylinder of air per deep diver down to 200 feet in case there had been a failure or more gas had been consumed than was planned. He met the deep divers at a specific time according to their decompression schedules. If all was well, he stayed above the deep divers and watched as they ascended and was required to stay out of decompression, himself. The shallow support diver carried one cylinder of EAN40 for each deep diver down to 110 feet. Again, if all was well, he took over watching the deep divers while the deep support diver returned to the boat to exchange his air cylinders for oxygen cylinders. The primary oxygen cylinders for the deep divers were usually staged at 30 feet along with extra air cylinders and the original deep support diver would meet the deep team there at the appropriate time. The boat support was constantly sifting through huge stacks tanks insuring that each support diver carried the correct tanks to the individual deep divers. Again the support divers continued to watch the deep divers until they were back on the surface and in the boat.

The exploratory divers were diving double aluminum 80s on their backs and used stage cylinders as appropriate. The exploratory divers were looking for cave entrances inside the Blue Hole to depths of 200 feet , exploring the Abyss cave (the one in front of the resort) and surveying and mapping some of the speleothems at 100 to 160 feet inside the Blue Hole. The deep teams also were looking for cave systems while exploring the bottom for speleothems and exploring the Abyss cave system.

The Results

It will be several months before the final results are in, however, the expedition was a tremendous success and Dr. Dill feels we have made the geological finds of the decade. There were no speleothems collected from the bottom, it appears that the bottom is completely covered by sediment which is pouring in from the edges at an accelerated rate, particularly on the north wall that is more popular for sport divers. This has made the center the deepest point in the Blue Hole unlike most other sink holes that have a debris cone in the center that is the shallowest point.

There is a high production of calcareous organic sediment all around the upper rim of the blue hole that is produced by a lovely algae, Halimeda. It looks like a plant with "leaves" joining each other in a string. It is abundant in the Caribbean and often given little notice by divers. If you look carefully, many of the "leaves" at the ends of each string are white. It is these platelets that can be seen covering the bottom producing sand. When these plants die their remains rain down from the overhanging upper lip of the blue hole and have built up a ring shaped mound on the outer circumference of the bottom. This mound slopes steeply to the wall and out towards the flat, featureless and deeper center of the blue hole. On the outer edge where the mound makes contact with the bedrock exposed at the bottom of the wall below overhangs at the upper lip of the cavern.

The team videoed flow stone at 320 feet and collected samples for dating from the surface of some of the walls located near the bottom. Initial inspections in the field of these samples determined they might be from past dunes and holes in the samples were thought to be from root systems of plants that were present on the dune.

Much to the teams surprise, there were no speleothems below a depth of approximately 320 feet. This was also near the depth of a sharp thermocline and turbid hydrogen sulfide layer. In a layer like this, the water does not contain dissolved oxygen and therefore, most life cannot survive within it.

The sediment samples, obtained by taking two, three inch diameter push cores from the center at 405 to 408 feet, also had a strong odor of hydrogen sulfide. Since the Great Blue Hole of Belize acts as a giant sediment trap, the cores will be tested by Eugene Shinn at the U.S. Geological Survey in St. Petersburg, FL., where he will be looking for the distinctive dust from the Sahara Desert.

Surveying of the speleothem gallery on the southwest side of the Blue Hole was started. Thirty three stalactites or columns over approximately 400 feet along the rim were charted for relational distances and azimuths. There is no known prior survey or count of the speleothems in this area. This information will provide the basis for full maps of the gallery.

The Abyss cave in front of the resort was explored and videoed. The team descended down a debris mound (similar to most sink holes) to a depth of 485 feet (now the fourth deepest dry or flooded cave in Belize) and it appears to be a similar system to the Blue Hole with only a small karst window for an opening leading to a huge open room. The exploratory team believes the system has an approximate depth of 500 feet. The Abyss is considered to be an extremely important find because it, like the blue hole, is on an atoll with little or no major river run-off to provide the fresh water needed to dissolve away large amounts of limestone to form a large cavern by dissolution alone. A major question facing the project scientists was how did this dissolution take place if it cannot be attributed to fresh water? We may have discovered just such a process in our dives. It is probably related to the geologic and oceanographic conditions existing in the interior of giant limestone platforms such as the Bahamas, Yucatan and the atolls off Belize.

Probably the most exciting find and recovery was a cave that was littered with calcified crab shells and fish vertebrae, as well as, 4 large turtle skeletons. This cave has an entrance at 200 feet below a ledge. The entrance goes up to a chimney at about 165 feet that leads up to a beautifully developed side cave with a nearly flat bottom at a depth of 135 feet. This passage is very low and extends for over 175 feet. Air photos of this region show that this cave is related to a long coral ridge with a similar direction. The ridge in shallow water has a strikingly different shape and is an anomalous feature compared to the numerous round and oblong patch reefs that dot the upper surface of Lighthouse Reef atoll. It is interesting to note that there is a world wide terrace and sea level features throughout the world at this same depth.

Terrence and Matt ("the German") surveyed and videoed this cave. They also collected samples of a stalactite and stalagmite from a remote section of the cave at 133 feet. These samples are in a remarkable state of preservation. The broken ends show several cycles of formation and a layer of marine carbonates deposited after sea water flooded the cave.

The determination of the age of these cycles by radio carbon dating will be analyzed using a new mass spectrometer at the University of New Mexico by Dr. Yename Asmerom, a specialist in isotope geochemistry, who was also a member of the expedition.

We all look forward to the results of the dating tests and other research. We are confident that the results of this self supported and sponsored expedition will provide the basis for future long term funding of the Cambrian Foundation and funding for similar scientific projects that utilize deep technical diving with trimix to go to areas not possible before this relatively new technology existed. We plan to go back not only to Belize but other areas where submerged karst and caves provide a means to study the anatomy of giant carbonate limestone regions.

Expedition Personnel

The deep (trimix) divers
  • Terrence Tysall, President, the Cambrian Foundation, technical instructor, expedition leader
  • Ken Furman, Treasurer and Secretary, the Cambrian Foundation, expedition organizer
  • Andreas "Matt" Matthes, The German "at large", the diving Mercedes, technical instructor, Mexico
  • Dr. Andrew Pitkin, Deputy Director of Hyperbaric Medicine for the Royal Navy, decompression schedules
  • Mike Armstrong, USS Monitor Project Director for the Cambrian Foundation
  • Steve Newman, Owner of Choo Choo Dive Center, gas blender, provider of the booster and molecular sieve column for O2 Clean air
  • Kyle Creamer, Owner of Diving Enterprises, Ltd., gas blender, technical instructor
  • John Chluski, Owner of Swift Current Productions, deep video technology

The Support and Exploratory divers
  • Tim Gallagher, Network engineer
  • Chris Johnson, Assistant Recreational Manager, Blizzard Beach Water Park, (Disney)
  • Dr. Clyde Martin, Dive physician, gas blender, pseudomonas bacterial studies
  • Cindy Creamer, Owner of Diving Enterprises, Ltd., assistant for the scientific team, chief still photographer and documentation of expedition
  • Brett Wolfenbarger, Staff, Light House Reef Resort

The Scientists
  • Dr. Robert Dill, Dill GeoMarine Consultants, Professor of Geology, Humbolt State University and University of South Carolina, geologist for 1970 Cousteau Expeditions and a resume that would fill a small book
  • Dr. Anthony Jones, Jones Oceanic Consulting
  • Dr. Yemane Asmerom, Radio Carbon Dating/Mass Spectrometer, University of New Mexico

The video specialist along with John Chluski, Terrence Tysall
  • Julie Kaye, Owner of Swift Current Productions, video, land and underwater, video coordinator
  • Andrew Stockbridge, Manager, Light House Reef Resort, boat captain

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