fbpx
Connect with us

Exploration

Diving Into History With Thailand’s Sira Ploymukda

Certifiable Venezuelan dive geek Carlos Lander explores the discoveries of Thailand’s underwater archeology research team headed by resident expert Sira Ploymukda, who’s been involved in at least ten shipwreck excavations. Their findings are shedding light on Thailand’s role in early transoceanic commerce.

Published

on

by Carlos Lander

Lead image courtesy of Siwat Worachananant and Sira Ploymukda

Thailand is famous for its stony beaches, picturesque scenery, and outstanding dive sites, including reefs, deep drop-offs, wrecks, walls, and caverns. Most of the must-see sites are in the Andaman Sea along the west coast.

Thailand has a splendidly nuanced cultural heritage, one that has recently been explored in unprecedented depth by a new generation of marine archaeologists.

Despite what you may assume, marine archaeology is not about shipwrecks—it’s about human development. Luckily, Thailand is home to a resident expert: Sira Ploymukda, head of the country’s underwater archaeological research team.

Photo courtesy of Siwat Worachananant and Sira Ploymukda

Ploymukda (pronounced ploy-mook-da) is an expert archaeologist, who studies traditional artifacts, ports, and harbors. During his studies, he unearthed substantial evidence indicating that Thailand was a transoceanic corridor and a trans-peninsula route; his research also explores ship construction technology and its role in Thailand’s archaeological history. These subjects constitute his doctoral dissertation, the defense of which has, unfortunately, been delayed by the pandemic. 

Ploymukda has also contributed to the excavations of at least ten shipwreck sites in Thailand. He was trained in the diving arts by explorer and instructor Bruce Konefe who also leads shipwreck discovery teams in the country. As the head of the field department of Thailand’s Underwater Archaeology Division for over ten years, Ploymukda has taken the time to explore and study new archaeological sites. Over time, his efforts have paid off.

Ploymukda and his team are exploring newly-discovered wrecks in an effort to determine the ranges of each particular ship based on their design, the cargo content and type, and the average payload weight in order to calculate the economic value of the cargo that was moved across cultures by these particular ships. While the Thai government is engaging with neighboring countries to publicize the importance of this academic exploration, divers are taking the lead in these research efforts. Their first major task: finding the wrecks in the first place.

Discovering New Shipwrecks 

Ploymukda describes two basic methods for finding shipwrecks: active and passive. Many countries utilize satellite images to search, but sonar is more effective for exploring a specific area. Once the team has a lead on a new wreck based on sonar images, a diver or a remote underwater vehicle (ROV) is sent to verify what’s down below. This is active searching.

The second method, passive searching, happens when a village fisherman catches his net or line on the ocean floor, losing it or tearing it apart. This indicates that there is something on the sea floor that’s not supposed to be there—an object big enough to get a net stuck. At this point, an archaeologist becomes a detective. 

While an archaeologist’s role is to explore, exploration is costly. So, one way to reduce expenditures is asking fishermen to report these kinds of incidents. Archaeologists or explorers gather as much information as possible from fishermen for the purpose of determining if a potential site is worth exploring (economically speaking).

In the end, there’s only one way to be sure of what’s “down there,” and that’s diving.

Photo courtesy of Sira Ploymukda and the Ministry of Art’s

Once researchers decide to investigate a site, they closely guard their leads; looting is a big problem in Thailand. Since most site robberies take place in shallow waters, dive teams tend to excavate and survey sites at around 40-70 m/131-230 ft, making them more difficult for robbers to access. Ploymukda dives with a rebreather and often uses trimix (an oxygen, helium nitrogen mix to reduce narcosis) as diluent.

The site location remains confidential until all data and artifacts are collected, but for organizational purposes, it’s customary to name each wreck after the nearest port. GPS coordinates aren’t published until after excavation is complete. 

The present study includes the wrecks below:

Table courtesy of Sira Ploymukda

Boots, err Fins On the Ground 

Underwater archaeology is a scientific diving effort with forensic diving elements, meaning that divers must adhere to written protocols and prepare appropriately-sized teams. In general, a complete team is composed of one land team—including an officer who is responsible for all planning and contingencies—and two diving groups, one to perform the dive and the other to serve as a backup team. The backup team needs to be ready to enter the water in less than one minute in case of any emergencies. 

Depending on the depth, a bottom time of 30 minutes plus decompression is customary. But, the officer is responsible for adjusting the plan based on a variety of factors, including weather conditions, currents, or depths. 

Ploymukda explained that, in the past, the location of a shipwreck was manually recorded using a compass, a nautical map, and depth gauge, and wrecks were only sketched—a far cry from today’s sophisticated GPS, photogrammetry, and modeling technologies. Along with recording the specific location, divers also survey the sites, collect samples, and take measurements, videos, and photographs. 

In the event that the team salvages any artifacts, they take immediate action to prevent those artifacts’ decay.  Tanks of saline on the boat mimic the artifact’s familiar underwater conditions until the object is sent to a lab facility for further conservation work. Fortunately, in Ploymukda’s case, he has his own lab. 

The first step in the lab is removing the salt from an artifact by putting it in distilled water. Depending on the artifact, other processes are undertaken; for example wooden findings are saturated with a wax-like material, vacuum-sealed, and freeze-dried. Then, artifacts are sent to a separate lab for dating, which is paramount to the next step: building a narrative.

Building the Story

Archaeology’s purpose is to construct a narrative: a story that fits into historical context. But, it’s not that simple underwater. Data collected from the site during a dive is integral to discovering that context, but those data aren’t the only useful tool. 

Context, to an archaeologist, includes the place where an artifact was found, the soil, the site type, the layer of soil the artifact came from, what else was found in that layer, and numerous other minutiae. A shipwreck, unless it was found in a harbor, is much more difficult to put into a context than a site on land; luckily, Ploymukda’s research expertise fills in some crucial gaps.

The design of each individual ship serves as an indicator of their travel range, their cargo content and type, and the average payload capacity. These data, along with historical manuscripts or logs, are particularly important tools for cultural context identification. 

The ancient peoples of the Southeast Asia region were seafarers, and they knew how to use various types of sailing vessels for long-distance voyages. But, Ploymukda and his team are trying to understand the intercultural exchange that occurred as a result of these sailing routes in the Andaman Sea and the Gulf of Thailand. 


Their investigations uncovered two types of shipwrecks with distinct construction and rigging, which are integral details when determining a ship’s commercial route. Shipwrecks found were classified using ship typology, building technique, and rigging styles to pinpoint the sailing routes; once a ship was classified, the distance she could travel, the number of people she could carry and the amount of cargo she could hold could be estimated.

The shell base shipbuilding technique originated in Egypt, and was widely adopted throughout the Indian and the Pacific Oceans, as confirmed by various wreck recoveries. Frame base, however, is a technique from the east, popularly used in Chinese junk ships. Between 2008 to 2018, 46 shipwrecks were excavated in the Andaman Sea and the Gulf of Thailand, and researchers encountered both the shell base and frame base in their explorations. 

In addition, researchers observed different rigging techniques. Rigging refers to the system of ropes, cables, and chains that support a sailing ship. According to archaeological evidence, rigging implements have been in use in the Pacific Ocean for the past 3,000. Two rigging techniques were discovered: Lateen and Junk rigs. Lateen rigs were found in sewn boats in South East Asia. Junk rigs have been found in China; this is evidence of cultural interchange between China and Thailand.

A shell base boat. Photo courtesy of Sira Ploymukda and the Ministry of Art’s

A frame base boat. Photo courtesy of Sira Ploymukda and the Ministry of Art’s

As you can imagine, all this work takes time. Not only must researchers discover a shipwreck, salvage artifacts, and conserve them, but they also must study the wreck, associate it with a timeframe history, build a narrative theory, and test that theory. And, after all of that, many of the artifacts are sent to museums for display and further preservation.

In this line of work, you don’t just do research using books; to paraphrase Indiana Jones, “If you wanna be a good archaeologist, you gotta get out of the library.” In Ploymukda’s case, he has fulfilled that admonition entirely.

Ploymukda’s work is still ongoing. If you want to learn more about this project, you can visit the Fine Arts Department of Thailand online, where you can access the virtual museum  and contribute to the project.

A picture containing text, sport, water sport, swimming

Description automatically generated
Photo courtesy of Siwat Worachananant and Sira Ploymukda

Additional resources:

SEAARCH: Southeast Asian Archeology, Underwater Archaeology Division (Thailand)

Ancient Maritime Cross-Cultural Exchanges 

X-Ray: Ancient Wrecks Ming Pottery Wreck: Exploratory Expedition in the Gulf of Thailand

Other stories by Carlos Lander:

InDepth: They Helped Foment a Dive Computing Revolution: RIP Cochran Undersea Technology (1986-2020)

InDepth: ¡Oh Deco! ¡h Doppler!, O’dive: Evaluando la primera herramienta personal de seguridad para una “deco” conocida


Carlos LanderI’m a father, a husband, and a diver. I’m a self-taught amateur archaeologist, programmer, and statistician. I think that the amateur has a different mind set than the professional and that this mindset can provide an advantage in the field. I studied economics at university. My website is Dive Immersion.  You can sign up for my newsletter here.

Exploration

Confronting the Unknowns of Decompression with the First Electronic Rebreather

How did Electrolung inventor Walter Starck and his cronies decompress from dives to 100m/326 ft before the advent of dive computers or even constant PO2 tables? Dr. Starck explains his procedures and rationale. Deep stops anyone?

Published

on

By

by Walter Starck
Photos courtesy of Walter Starck

The design and manufacture of the first commercially available, electronically regulated closed circuit mixed gas rebreather in 1968 presented a multitude of problems to be solved in the design and manufacture of the device itself.  Successful development and production of the Electrolung presented an additional problem. Decompression tables were limited, and none were available for a constant partial pressure of O2 with a varying percentage of inert gas as occurs in an electronic rebreather. The US Navy tables were the only heliox tables readily available. Those used in the offshore oil industry were all treated as commercial secrets by the offshore diving companies. Decompression computers had not yet been invented. 

To start with, I interpolated from the US Navy helium tables for an equivalent partial pressure depth for the Electrolung.  Although, by today’s standards, this may seem unacceptably risky, it was less so than may appear. If immediate recompression is available at the first symptoms of any decompression sickness, progression to more serious levels is rare. When recompression is delayed for several hours, or more, to get to a chamber there is a high probability of increasing tissue damage requiring extended treatment and lengthy recovery or permanent impairment. 

A young Walter Starck about to dive in the Coral Sea with his Electrolung in 1971.

My research vessel, El Torito, was equipped with a large (42’’ x 12’) double lock recompression chamber which could comfortably accommodate two persons, or even three if needed. The inner lock was kept pressurized to 30 m/100 ft, so getting to 18 m/60 ft of pressure could be accomplished in less than a minute by just getting in, closing the outer door, and opening a valve to let the main inner chamber equalize with the entrance chamber. An oxygen rebreather also provided for 100% O2 decompression without the fire risk of pressurising the chamber with O2. Having a chamber immediately available reduced the risk of experimenting with decompression profiles to an acceptable level. In practice, there was only one incident where the chamber was needed, and that involved pushing the limits with a repetitive dive to 60 m/200 ft with only an hour surface interval.

While getting into the matter of decompression, I came across an interesting study by the Australian physiologist Brian Hill, who found that the pearl diving industry in northern Australia had developed (by trial and error, including numerous fatalities) a mode of decompression that started deeper, ascended slower, and ended deeper but was faster overall.  Based on this, some relevant physics, and Hill’s own extensive lab work, he proposed a theory of what he called thermodynamic decompression. In this regard, he believed that the idea of avoiding bubble formation by keeping within a hypothetical limit of supersaturation is incorrect, as any degree of supersaturation results in a gas phase beginning to form as a thin film at tissue surfaces, which then begin to coalesce into sub-symptomatic bubbles.



In his view, the conventional tables were generating sub-symptomatic bends by allowing divers to ascend too quickly and then having to spend a lot of (decompression) time to prevent them from growing into symptomatic bends. If the bubble formation is avoided to begin with by allowing the inert gas to escape through the dissolved gas saturation window provided by the ability of tissues to metabolize O2, decompression can be optimized. 

Diver with Electrolung.  Note pink Baralyme absorbent.  The acrylic bubble was being used for a shark cage.

My study of his material left me with the impression that it was well founded, so I began to titrate decompression toward that direction. This led into a series of 92 m/300 ft dives with 15 minutes descent and bottom time, a slow 10 m/30 ft-per-minute or slower ascent time, a couple of stops for about two minutes at around 46 m/150 ft and 22 m/75 ft, finishing with 15 minutes on pure O2 at 10 m/30 ft. On different occasions, but not at the same time, three other individuals accompanied me, all without DCS in some 30 such dives.

The effort, resources, liability risk, and limited economic potential involved in endeavouring to develop a full set of tables of this kind, as well as my own prime interests in marine science and exploration, ruled against further pursuit in this direction. However, a few years later when I arrived in Australia with El Torito, I got in touch with Brian Hills and had the opportunity to spend several days with him in Adelaide.  He went on to a distinguished career in decompression physiology at several institutions in the US and UK. 

See accompanying Story: Electrolung: The First Mixed Gas Rebreather Was Available to Sport Divers in 1968

Additional Resources:

For more on Hills and his thermodynamic theory, see: Brian Andrew Hills 

Wikipedia: The US Navy’s Thalmann Constant PO2 Algorithm

NEDU: DEVELOPMENT AND VALIDATION OF 1.3 ATA P02-in-He DECOMPRESSION TABLES FOR THE MK16MOD1 UBA

InDepth (Four part series): Decompression, Deep Stops and the Pursuit of Precision in a Complex World by Jarrod Jablonski

UHMS: PROCEEDINGS: DECOMPRESSION AND THE DEEP STOP (2008)

Immersed: The International Technical Diving Magazine (Winter 1998), Starck, Walter 1998. In Water Recompression: Problem or Solution? by Walter Starck. Reprinted courtesy of DIVER mag.

InDepth: A New Look at In-Water Recompression (IWR) 


Walter Starck is one of the pioneers in the scientific investigation of coral reefs. He grew up in the Florida Keys and received a PhD in marine science from the University of Miami in 1964. Since 1978, his home has been in north Queensland, Australia. Throughout his career in marine biology, participating in expeditions around the world,  Dr. Starck has been extensively involved with development of the technology required to facilitate his activities. In several instances patented inventions and commercial products have resulted. In addition to the optical dome port and the Electrolung other noteworthy achievements in this area have been: The Bang stick—a hermetically sealed underwater firearm for hunting and defense, underwater housings for numerous cameras and instruments, underwater lighting systems, a multipurpose commercial waterproof electrical connector,  design of the unique research vessel El Torito, a 9 meter high-speed diving launch, a 24 passenger eco-tourism vessel, and the Oceanic 8000 Longboat.  The longboat was a long narrow high efficiency powerboat inspired by the efficiency of the log canoes of the Solomon Islands.  He has also built and flown an amphibious aircraft of advanced canard wing design using high technology composite materials. Recently (Aug 2017) he was senior author on an extensive update on the Alligator Reef study that brought the total species list for that locality up to 618 species.

Dr. Starck has authored over 100 articles and books, which include numerous technical and peer reviewed scientific studies as well as many articles in leading popular publications. His photography has been widely published in conjunction with his writing, and he has produced nearly 20 films and videos. Throughout his extensive career, he has managed to inspire not only admiration, but also the ire of some detractors who have taken umbrage at his efforts to inject what he believes to be “a rational perspective on human ecology into the eco-mania that has become epidemic in our struggling Western economies.” His criticisms of the “poor science and blatantly false claims widely used to support various environmental agendas” have earned him some criticism.

Continue Reading

Thank You to Our Sponsors

Subscribe

Education, Conservation, and Exploration articles for the diving obsessed. Subscribe to our monthly blog and get our latest stories and content delivered to your inbox every Thursday.

Latest Features