The Mechanisms and Challenges of Marine Archaeology

Marine archaeology, unlike traditional archaeology, was not considered a scientific discipline until the 1960s. It is most often concerned with shipwrecks but can be applied to any study or excavation of artifacts on or below the ocean floor. This area of research comes with its own unique set of challenges, as many of the standard archaeological methods simply cannot be applied. It is far more labor intensive and expensive, with common obstacles including poor weather conditions and tidal complications (Blakemore, 2019). Despite these roadblocks, marine archaeology provides insight to huge swaths of history lost to the ocean’s depths.

Side Scan Sonar, USGS

Many different methods and strategies are used for underwater excavation. For initial surveillance of the ocean floor’s topography, side scan sonar has long been the preferred operation. Unlike standard sonar, which scans in a conical shape, side scan sonar scans in two directions at once, both vertically and laterally. This allows for a far sharper resolution of depth imaging (Egenrieder, 2014). For coastline detection and mapping, satellite imaging is also employed (Blakemore, 2019). Many of the same tools that are used by archaeologists on land can be used underwater, such as hand trowels, but others are very different (Adovasio, Hemmings, 2012). While archaeologists on land scoop dirt onto a screen to sift through it, underwater archaeology requires a massive vacuum cleaner-like machine to suck sediment off of the seafloor at a rate of 600 gallons per minute and then press it through a floating screen deck to sift through the debris (Adovasio, Hemmings, 2012). Many organic materials, such as wood, bone fragments, and plant fibers are better preserved underwater than on land, but the process of extracting these fragile materials from the seafloor requires significant caution (Adovasio, Hemmings, 2012). They must be carefully removed, brought to the surface, stabilized, and often refrigerated to prevent decomposition caused by exposure to the light and air that they likely haven’t seen since they sunk to these depths (Adovasio, Hemmings, 2012).

Sediment vacuum in use on an underwater archeological site, Global Foundation For Ocean Exploration

Underwater archaeologists must undergo additional training on top of their credentials as archaeologists. Diving training is essential, as well as many hours of practice for the specific conditions of an underwater archaeological site (Kenyon, 2020).  It is easy to accidentally damage the site when you are met with environmental challenges like quick moving currents, wildlife, and unexpected weather patterns (Kenyon, 2020). Risks like these can make this profession a dangerous one, so abundant caution and years of practice are the key to successful research outcomes. Still, this research remains invaluable. Over two thirds of the earth’s surface is covered with water, oceans and rivers that humans have been crossing and tossing items of precious historical significance into for as long as we’ve been here. The trouble lies in accessing them.


“Maritime Archaeology”. Archaeology: National Marine Sanctuaries Maritime Heritage Program.  NOAA.

 Blakemore, Erin. August 2, 2019. “How Underwater Archaeology Reveals Hidden Wonders”. National Geographic. National Geographic.

Egenrieder, Tim. June 19, 2014. “A Beginner’s Guide To Side Scan Sonar”. On The Water. On The Water.

Kenyon, Kimberly. April 29, 2020. “What Is Underwater Archaeology?”. Submerged NC. North Carolina Office of State Archaeology. 

 Adovasio, J.M.. Hemmings, C. Andrew. 2012. “Underwater Archaeological Excavation Techniques”. Exploring The Submerged New World 2012. Ocean Exploration NOAA.

Links To Further Reading:


The Tollund Man and Other Bog Bodies

“Bog Bodies”, or cadavers found preserved in the peat bogs of northwestern Europe, are some of the most well preserved human remains discovered in archaeology. Because their bodies and belongings are often so intact, they garner quite a bit of speculation as to the circumstances of their life and death. Many have visible wounds and clear indications of violent death, often as products of religious sacrifice.  We are given a shockingly detailed piece of a much larger and more complicated context that is not fully understood. 

Peat bogs are composed of a tightly packed matrix of sphagnum plants. When these plants die, they release a sugar compound known as sphagnan that neutralizes nutrients in the water. This makes peat bogs a difficult environment for decay-causing bacteria to grow. Sphagnum also releases acid into the water, which ‘tans’ the cadaver’s skin, making it leathery and more resistant to damage (Moesgaard). This is why the faces of some bog bodies are so striking, as you can see every little detail of their expression in death, like in the case of the Grauballe man (Kuiper, Kathleen). 

Peat Moss

The Tollund Man is the most well preserved bog body to date, with even the sheepskin hat on his head intact. His head is topped with long hair in a braid, and only his arms and legs appear skeletal. He was found in 1950, and like many bog body discoveries, those who first found him thought he could have died quite recently. In reality his remains have been dated to 2,400 years ago (McGreevy, Nora). Several parts of his body have been studied, including attempts at DNA testing of samples collected from his femur and the base of his skull.The contents of his stomach revealed that his last meal was of porridge and fish (McGreevy, Nora).

A raised bog

All of these details can be known about bodies like the Tollund Man’s, but the question is, should we be invading his resting body to find them out? Information about his environment and living habits is invaluable when collected, to better understand the culture and world that he lived in so long ago, but is that enough? Did those who placed him in his resting place imagine that he would be on display in a museum for over half a century now? The ethics of unearthing and displaying human remains are quite complicated, as with any case where burial is involved.


McGreevy, Nora. July 22, 2021“What Did Tollund Man, One of Europe’s Famed Bog Bodies, Eat before He Died?”

Kuiper, Kathleen. “9 Noteworthy Bog Bodies (and What They Tell Us).” Encyclopædia Britannica.

Guerra-Doce, E., C. Rihuete-Herrada, R. Micó, R. Risch, V. Lull, and H. M. Niemeyer. April 6, 2023. “Direct Evidence of the Use of Multiple Drugs in Bronze Age Menorca (Western Mediterranean) from Human Hair Analysis.” Nature News.

Magazine, Smithsonian. May 1, 2017. “Europe’s Famed Bog Bodies Are Starting to Reveal Their Secrets.”

“Moss Magic – Sphagnum Preservation.” Moesgaard Museum. Accessed October 1, 2023.

Further Reading: