When I asked my mum and dad to picture a maritime archaeologist, they immediately described a diver fluttering about underwater searching for lost relics on the seafloor (Figure 1). To those in the know, the archaeologist/diver would resemble something quite different; an individual meticulously excavating and recording a submerged archaeological site. But can the definition of a maritime archaeologist be as simple as a diver that straps a tank (or two) to their back? Before any work underwater is carried out, the type of diving apparatus that will be used must be taken into consideration. Without the diving component archaeology cannot be conducted underwater. I will discuss the different types of diving equipment necessary to carry out a pre-disturbance survey and excavation in an occupational setting, but will limit the topic to standard compressed air diving. Other diving classifications such as NITROX and mixed-gas diving can be used, but are limited to trained professionals and the offshore oil and gas industry. The most common type of diving in maritime archaeology is compressed air diving.
Diving apparatus: SCUBA & SSBA
What is the difference between SCUBA (Self Contained Underwater Breathing Apparatus) and SSBA (Surface Supply Breathing Apparatus)? Apart from both acronyms containing the words ‘Breathing Apparatus’, the difference lies with the first two words, ‘Self Contained’ and ‘Surface Supply’. SCUBA is a self-contained unit in which the diver relies on a tank to deliver compressed air through a mouthpiece (Figure 2). Commercially developed in the 1950s by Jacques-Yves Cousteau and Emile Gagnan, SCUBA allowed people to explore the underwater world and by doing so, paved the way for maritime archaeology to develop into the discipline it is today (Green 1994: 2–4; Hosty and Stuart 2001: 5; Muckelroy 1978: 10–22).
SSBA is also a compressed air system, but exhibits slightly different features (Figure 2). The diver receives air from the surface from either a bank of compressed air tanks or an air compressor. The air is usually breathed through an AGA mask, band mask, or hard hat (Figure 3). A hard hat is a solid, one-piece helmet, usually associated with underwater construction. It provides head protection for the diver from falling debris. A band mask is made up of a solid face plate similar to the hard hat, but has a soft neoprene hood. An AGA mask is a full face mask secured to the diver’s head with a series of straps. SSBA can trace its origins back to early 19th century hard hat diving, and was an essential element of what is regarded as the first maritime archaeology survey—an investigation of crannogs in Loch Ness, Scotland in 1908 (Muckelroy 1978: 10, 12).
Which diving apparatus for what underwater method?
Different diving equipment will have advantages and disadvantages, depending on the type and extent of tasks that need to be performed. From my experience, SCUBA provides the freedom to cover a large area, as would be needed to conduct a pre-disturbance survey. The objective of a pre-disturbance survey is to survey and record a site as it appears on the seabed (Green 2004: 88; Tripathi 2005: 6). For more information on pre-disturbance survey methods see Lauren Davison’s blog post.
A diver with a ‘Self Contained’ breathing unit is free to travel as far as they want, subject to certain physiological and environmental restrictions. These include the strength of currents and amount of compressed air available. SSBA, by contrast, is restricted by the length of the equipment’s umbilical (which contains the air hose, communications link, etc.). Planning helps, but it is difficult to know how much umbilical is needed when the extent of the site is unknown. Other considerations for occupational diving include:
- Environmental conditions (visibility, entrapment, water temperature, underwater terrain)
- Hyperbaric/physiological (depth, frequency, duration, prior fitness)
- Associated activity (manual handling, boat handling, dive platforms)
- Other (dangerous marine animals, shipping movements)
Unfortunately, not all forms of diving equipment are affordable and/or available. In instances where only SCUBA equipment is available, the archaeology fieldwork plan will need to be adjusted to correspond to SCUBA’s limitations. Some of these limitations include the number of divers needed to conduct fieldwork, dive duration, and surface intervals between dives.
SSBA is used if the equipment is available and/or required under Australia’s Occupational Diving Standard (AS/NZS2299.1). This standard requires the use of SSBA when a dive project includes the use of surface machinery that is not under direct control of one or more divers, such as the water dredge or airlift. Both the water dredge and airlift are designed to remove spoil from the area of excavation and deposit it away from the site. Both have their advantages and disadvantages; for a discussion of this topic see Green (2004), and for more details about underwater excavation methods see Marc Brown’s blog post.
Maritime archaeology projects within Australia that involve commercial interests and the use of equipment such as dredges must utilise SSBA (Figure 4). Maritime archaeologists must hold an accreditation with the Australian Diver Accreditation Scheme (ADAS) to dive using SSBA. SSBA must also be used where participating divers undergo physical exertion. Projects reliant on SSBA must consider such factors as the use of a compressor, length of SSBA umbilicals, available bottom time, and the need for fuel and qualified personnel (a team of five is required for a two person SSBA dive team).
During each diving day both SSBA and SCUBA equipment must be set up, broken down, and tested on a daily basis. The equipment must also be maintained, usually on an annual basis. This is costly in terms of time and money, particularly for projects that are operating on a tight schedule and budget. Ultimately, both SCUBA and SSBA enable maritime archaeologists to undertake any underwater task, provided it meets occupational standards.
Before commencing archaeological investigations underwater, it is important to consider the apparatus best suited for the job and whether it complies with occupational standards. Because every site is different, dive equipment and planning will undoubtedly vary. Limited access to diving equipment may force a project to work with what is available and plan diving operations accordingly. With these factors in mind, the question remains: is a maritime archaeologist simply a mask and a tank? The answer is no, as there is a lot more to conducting maritime archaeology than just fluttering about underwater.
2008 Surveillance and Protection of Underwater Archaeological Sites: Sea Guard. Protecting Underwater Archaeology, Press Room. Electronic document, http://www.acoustics.org/press/155th/akal.htm, accessed 15 October 2013.
2004 Maritime Archaeology: A Technical Handbook, Second Edition. Elsevier Academic Press, USA.
Hosty, Kieran and Iain Stuart
1994 Maritime Archaeology over the last twenty years. In Maritime Archaeology in Australia: A Reader, edited by Mark Staniforth and Michael Hyde, pp.5-12. Southern Archaeology, South Australia.
1978 Maritime Archaeology. Cambridge University Press, Cambridge.
Submarine Manufacturing and Products
Kirby Morgan 18B Band Mask. Electronic document, http://www.smp-ltd.co.uk/product/productid/193/productname/Kirby-Morgan-18B-Band-Masks/, accessed 3 October 2013.
2005 Marine Archaeology (Recent Advances). Agam Kala Prakashan, India.