The most obvious and crucial step to broadening a diver’s capabilities is providing an air or a mixed-gas supply that will prolong his/her stay under the water. Diving operations can be conducted with the following diving systems:
- SCUBA (Self Contained Underwater Breathing Apparatus) diving systems; The diver uses a portable self-contained gas supply
i) Open-circuit systems
ii) Closed-circuit systems
iii) Semi-closed circuit systems
- Surface Supplied diving systems; The gas is provided from the surface to the diver via a flexible hose
Diving history, a brief timeline
The transition from the ancient diving devices and methods to the modern and sophisticated diving systems took many centuries. New inventions accompanied by significant physiological discoveries made it possible for the man to explore the deep ocean.
Earliest records of underwater activities
4500-2000 BC: The accumulation of seashell artefacts at prehistoric living sites indicates that breath hold divers collected food (and other products) from the sea. Earliest records are of Cretan sponge divers (3000 BC) and diving activities for oyster pearls in China (2200 BC).
1194-1184 BC: Military breath hold divers were used during the Trojan War to sabotage the ships, by boring holes in the hulls or cutting the anchor ropes. Divers also performed underwater construction activities in an effort to build underwater defences around the ports.
ca. 900 BC: Relief carvings show Assyrian combat swimmers crossing rivers using inflated animal skins as flotation devices. It was believed that these devices were used as breathing sets, but further examination suggests that the air-filled sacks were used as a floatation aid (see illustration below).
480 BC: From a very early date divers also engaged in the retrieval of goods that were lost at sea. The Persian king Xerxes is known to have given such a commission to a Greek diver named Skyllias.
“…there was in that camp a man of Skione named Skyllias, as a diver the best of all the men of that time, who also in the shipwreck which took place by Pelion had saved for the Persians many of their goods and many of them also he had acquired for himself…” - Herodotus’ Histories, Book VIII
332 BC: Alexander The Great uses military divers to perform underwater demolition activities during the siege of Tyre. There is a legend in which Alexander the Great is being lowered underwater in a barrel (diving bell). The device was called Colimpha. The interesting thing is that the legend appears both in western European medieval texts and in Islamic ones.
4th century BC: Aristotle describes the use of the snorkel (breathing tube): “Just as divers are sometimes provided with instruments for respiration, through which they can draw air from above the water, and thus may remain a long time under the sea, so also have elephants been furnished by nature with their lengthened nostril…” (Parts of Animals, 350 BC). Aristotle also described the function of the diving bell, “… they enable the divers to respire equally well by letting down a cauldron, for this does not fill with water, but retains the air, for it is forced straight down into the water.”
215-160 BC: Greek divers are used at the siege of Syracuse to construct underwater defensive obstacles. An early version of commercial diving starts to develop, as the salvage industry begins to develop in all Mediterranean harbours.
7th century AD: Roman salvage divers, the Urinatori, are used to rescue sunken cargo. Their work was regulated by law, the Lex Rhodia.
Renaissance diving equipment
1500s: Leonardo Da Vinci designs several diving devices consisting mainly of breathing tubes connected to a facemask and to a float at the other end. Later attempts on constructing breathing apparatuses were based on his sketches.
The Enlightenment Era
The diving bell was the dominant diving device for the next centuries.
1616: Franz Kessler designs a diving bell. The bell was negatively buoyant so the diver could walk on the sea floor. The diver sat on an internal framework and the body of the bell was equipped with several small eye ports from where he looked through.
1640: Hans Albrecht von Treileben and Anders Peckel uses a primitive diving bell to salvage 42 cannons from the Swedish ship Vasa at a depth of ca. 30 metres.
1680: Giovanni Borelli, an Italian mathematician develops a rebreathing diving set. He believed that by recirculating the exhaled gas through copper tube cooled by seawater would purify it. He also experimented with fin and buoyancy compensating devices. Now the diver became more an underwater swimmer, than a sea bottom walker. His device was probably never tested, but it depicts an early version of a rebreather set (SCUBA), as well the use of fins.
1690: Edmund Halley develops a diving bell. In 1716 this design was redeveloped by the use of air-filled barrels to replenish the air supply.
1715: Lethbridge designs a diving device looking like a cylindrical barrel, which accommodated the diver, whose arms protruded through tightly sealed sleeves.
1788: John Smeaton, constructs the first modern diving bell. The structure was made of cast iron, and it was supplied with constant airflow provided from a hand-operated pump on the surface.
1834: William H. James designs a self-contained underwater breathing apparatus (SCUBA). The diver was wearing a helmet with compressed air flow in its interior. The air reservoir was fastened around the waist of the diver. According to James, the diver could stay underwater for as long as an hour using this outfit.
1837: Augustus Siebe introduces the standard diving dress with copper helmet and leaden weights, rubberized canvas suit and leaden shoes. The ‘standard hard hat’ is fed through a safe air pump operated by two individuals. The Deane brothers used this equipment in salvage operations around Britain. Simultaneously, similarly designed equipment was developed elsewhere, but worldwide the Siebe Gorman standard diving dress-and its versions-were the most successful. This outfit was used for diving operations until the last quarter of the 20th century.
1854: The first important example of an archaeological application where a tube supplied air to a diver, was the device that Count Adolphe von Morlot used near Morges in his settlement research in Lake Geneva. A hose, into which air was pumped through a very simple pump from the surface, was connected to a diving cap, similar to a ‘helmet’, closing around the diver’s head.
Understanding physiological limits
1878: Paul Bert publishes “La Pression Barometrique”. Not only did he demonstrate that nitrogen bubbles cause decompression sickness but he also recognised the existence of “silent bubbles” following decompression. He also described the acute toxic central nervous system effects of oxygen.
1908: JS Haldane, Boycott and Damant publish “The Prevention of Compressed Air Illness”. They recommended staged decompression.
1915: The United States Navy (USN) Diving Tables is first published. Stillson and French conducted experimental research based on the original Haldane tables.
1926: A French Naval officer, Yves Le Prieur, patents the Frenez-Le-Prieur self contained diving apparatus. It was a diving set that had a cylinder of compressed air with a hand-regulated valve instead of a demand-valve. It fed a free flow of air into a mouthpiece or a full-face mask and was used with some success.
1943 Emile Gagnan, an engineer, and J Cousteau design the “aqua lung”. It contained a demand valve to regulate the air supply when the ambient pressure varies underwater.
1959: YMCA SCUBA Program is the first US organized course for scuba certification. Approximately 7 million divers are active worldwide and 500,000 more are training every year.
2005: Nuno Gomes uses self-contained underwater breathing apparatus (SCUBA) to dive to a depth of 318.25 metres. This is mankind’s deepest open water dive, until now, according to the official current world deep dive records.
2007: Free diver (breath hold diver) Herbert Nitsch dives to over 214 metres on a “No Limits” free dive in Greece. This became a world free diving record in the “No Limits” category. On June, 2012, in Santorini, Greece, he surpassed his own record, with a “No Limit” dive to 253.2 metres, but suffered from decompression sickness.
Mixed gas and saturation systems – Prolonged underwater stays
1964: The first larger habitat, SEALAB, is launched. The lab is put at a depth of 58 meters. The four saturation divers were called ‘aquanauts’. The aquanauts lived in SEALAB for 11 days, breathing a mixture of Helium and Oxygen, which becomes the standard for deep diving as HELIOX. Other missions including under water habitats were to follow later.
1966: Commercial saturation diving systems were quickly adopted by companies specializing in offshore industry and technology. In 1966 the first saturation dive was done in the Gulf of Mexico using a system designed by Westinghouse Electric Corporation, Underseas Division (Tom O’Neill and Alan Krassburg).
1992: Comex, a leading company in diving systems and technology, begins the HYDRA 11 project, including decompression chamber experiments. Teo Mavrostomos made a simulated dive to 2300ft (701m), which was a success and lasted 42 days. This was the deepest experimental human dive carried out so far and the main breathing gas mixtures were heliox and hydreliox (exotic breathing gas mixture of helium, oxygen and hydrogen).
Present: Diving companies, research facilities and Universities are intrigued by the saturation diving technology and new boundaries have been established. Research on diving medicine and physiology carries on constantly. Currently, the main underwater habitat devoted to science is the Aquarius Reef Base, which is located in the Florida Keys National Marine Sanctuary at a depth of ca. 20 metres. NASA, regularly, sends team of astronauts, engineers, technicians, and scientists for the NASA Extreme Environment Mission Operations (NEEMO) program. Main objective of the program is to conduct tests and research related to future asteroid exploration activities.
The last greater frontier on earth is the deep oceans of the world. It is also our last archaeological frontier. As new technology unlocks the ocean's depths, long lost, and in some cases forgotten, shipwrecks, sunken cities, and other submerged antiquitties have been discovered - John's Maritime History, Chapter 11.
Dive planning and risk management
The diving operations are being carried out in an environment, which is not designed to support life, as we know it. All the diving operations have an inevitable potential risk depending on the nature of each operation. Prior to a project, a Diving Project Plan (DPP) and a Risk Assessment (RA) need to be established in order to define any details associated with the diving operations, and minimize the risk(s), associated with them in acceptable levels. Both documents are obliged to fulfill the demands of regulatory agencies that have local authority at the area of the operations. The diving contractor is responsible for preparing the DPP and assessing the risks. His/her actions are constrained by the codes of practice and regulations covering all the activities associated with the project.
The British Health and Safety Executive (HSE) provides a wide range of activities from saturation diving in in the offshore oil and gas industry to recreational instruction by a professional instructor. There are five Approved Codes of Practice (ACoPs) that are published by the Health and Safety Commission:
1. Scientific and Archaeological diving projects. The Diving at Work Regulations 1997.
2. Commercial diving projects offshore. The Diving at Work Regulations 1997.
3. Commercial diving projects inland/inshore. The Divng at Work Regulations 1997.
4. Recreational diving projects. The Diving at Work Regulations 1997.
5. Media diving projects. The Diving at Work Regulations 1997.
The Diving Project Plan (DPP) describes the documentation, logistics (incl. the diving and nondiving personnel), nature of work and contractor’s operation rules, emergency arrangements, and techniques and equipment required. A vital part of the DPP is the Risk Assessment (RA) that is conducted to determine the hazards and risks related to the dive operations (scientific, commercial, and sport), and to address how these can be controlled.
A DPP should include information about the following:
- Definition of the mission objectives and the operational tasks
- Analysis of all data related to the dive site (environmental, emergency procedures, etc.)
- Dive teams and associated working practice
- Support personnel and associated working practice
- Equipment selection
- Risk assessment
- Procedures description for all phases
- Final preparations and safety checks
- Debriefing of the dive team, contractor, project manager, etc.
A key component of the DPP is the Risk Assessment (RA). It is an essential feature to be included in the DPP before any type of diving operation. Its main purpose is to address the potential hazards/dangers and safe ways of reducing accidents.
The basic steps to produce a Risk Assessment are the following:
- Identify the hazards related to the specific diving task and site
- Decide who might be harmed, affected, and how
- Evaluate the risks and define the the ways to control them
- Create a data of the findings and provide a copy to all team members
- Monitor and review the Risk Assessment
- Update the Risk Assessment as needed
See more here http://www.hse.gov.uk/risk/fivesteps.htm
After the hazards are identified, a convenient method to evaluate their potential is the Risk Evaluation Matrix*. Once the hazards are written down, the risks can be assessed. A 5 x 5 matrix combines seriousness/severity of the hazard and the probability of it happening. Risk is defined as the impact of the severity and the impact of the probability of a hazard. The first horizontal line (rows) represents the severity of the hazard and the first vertical line (column) is its likelihood of it happening. To be more specific:
Horizontal line definition:
1 = Trivial injury: Can be treated on site and do not prevent casualty from working; 2 = Minor injury: Injury or disease that keeps the casualty off work; 3 = Serious Injury; 4 = Major Injury: Serious injuries to a number of people; 5 = Death to one or more people
Vertical line definition:
1 = Extremely improbable occurrence, an accident can only occur under freak conditions; 2 = Improbable: A remotely possible but known occurrence; 3 = Possible: An occasional occurrence if an additional event takes place (not random); 4 = Probable: A fairly frequent occurrence; 5 = Highly probable: If work continues in this way, an accident is highly probable
For example, if a situation presents a hazard that is possible to happen and the consequences is a serious injury, then the risk would be medium.
*The above method is an example risk evaluation matrix. There are several altermative methods of producing a risk evaluation matrix.
Diver Training Agencies/Organizations
Recreational and Technical diving (listed alphabetically):
BSAC: British Sub Aqua Club - https://www.bsac.com/default.asp
CMAS: Confederation Mondiale des Activites Subaquatiques - http://www.cmas.org/
DDI: Disabled Divers International - http://www.ddivers.org/
GUE: Global Underwater Explorers - http://www.globalunderwaterexplorers.org/
IAHD: International Association for Handicapped Divers - http://www.iahd.org/en/
IANTD: The International Association of Nitrox and Technical Divers - http://www.iantd.com/
NAUI: National Association of Underwater Instructors - http://www.naui.org/
PADI: Professional Association of Diving Instructors - http://www.padi.com/scuba/
SDI: Scuba Diving International - http://www.tdisdi.com/
SSI: Scuba Schools International - http://www.divessi.com
TDI: Technical Diving International - http://www.tdisdi.com/
UTD: Unified Team Diving - http://www.unifiedteamdiving.com/
Scientific diving (listed alphabetically):
AAUS: American Academy of Underwater Sciences - http://www.aaus.org/home
ESDP: European Scientific Diving Panel - http://www.scientific-diving.eu/
Commercial diving (listed alphabetically):
HSE: Health and Safety Executive - http://www.hse.gov.uk/diving/
IDSA: The International Diving Schools Association - http://www.idsaworldwide.org/
IMCA: International Marine Contractors Association - http://www.imca-int.com/
Medicine, Research, First Aid
Alert Diver -http://www.alertdiver.com/: Digital magazine on diving safety.
DAN: Divers Alert Network -http://www.diversalertnetwork.org/: The diving industry’s largest association dedicated to scuba diving safety.
DAN Europe: Divers Alert Network Europe -http://www.daneurope.org/web/guest/home: DAN Europe (Divers Alert Network Europe) is an international non-profit medical and research organization dedicated to the safety and health of scuba divers.
DAN Medical Research Publications Database -http://www.diversalertnetwork.org/research/pubs.asp
DiversAlertNetworkTV - http://www.youtube.com/user/DiversAlertNetworkTV?feature=watch: Educational videos related to diving safety and medicine.
Diver Medic and Aquatic Safety Magazine - http://www.thedivermedic.com/magazine/: Magazine is dedicated to the health, welfare and safety of divers
Roubicon Foundation -http://archive.rubicon-foundation.org/xmlui/: Excellent digital repository of Diving and Environmental Physiology research.
The Diver Medic -http://www.thedivermedic.com/: Safety in diving and medical information to divers.
Konstantinos Alexiou (Greece) has earned graduate degrees in Marine Engineering and Maritime Archaeology. He is a Commercial Diving Instructor for the University of Southern Denmark (SDU), Denmark. His interests include diving medicine, the applications of diving science and technology, and the 3D reconstruction of naval vessels. Currently, he is undertaking training to become a Paramedic. Email: [email protected], [email protected]