The Laguna Nichupté archaeological rescue project in Cancun stands as a testament to the meticulous planning and scientific rigor that define underwater excavations. These operations provide invaluable insight into best practices for controlled underwater research. The methodology employed not only ensures the safety of divers but also reinforces the importance of preserving Mexico's submerged cultural heritage. Overseen by the Instituto Nacional de Antropología e Historia (INAH), this project highlights the intersection of archaeology, conservation, and modern infrastructure development. Through careful study and precision, researchers continue to safeguard the nation's historical legacy, even beneath the water's surface.
As on land, archaeologists can perform underwater archaeological excavation in a controlled manner. For this, a suction dredging system is needed, generated by a centrifugal motor pump of water, which is fitted with a metal head that, on the one hand, sucks the sediment and expels it on the other.
Water centrifuge used for underwater excavation
When activated, this system induces vacuum in the suction hose, allowing sediments to be removed from the seabed as if it were a vacuum cleaner. The exit hose is located outside the excavation area to prevent the removed sediment from being deposited again inside, which also generates poor visibility when the suspended particles are left.
Prior to underwater excavation, an inspection is carried out and sometimes it is necessary to acquire a cyclonic mesh to delimit the excavation area and thus protect against wildlife.
Presence of crocodiles near the underwater excavation site
The use of this mesh does not affect excavation maneuvers and, due to its portability, can be used in several surveys. In this project, we worked on the Nichupté lagoon in Cancun, prior to the construction of a vehicular bridge, so we had the excavation coordinates, which were loaded into a GPS to locate more accurately the sites where the excavation would be carried out and thus be able to install the mesh.
Team installing the cyclone mesh prior to excavation
Once the cyclonic mesh has been installed, the installation of the previously assembled grid is given way, which has measurements of 2 m by 2 m. The grid (as seen in the cover photo) is a key part of carrying out a controlled underwater archaeological excavation.
It serves as a reference for divers to know the limits of the survey; it can be done with different materials, such as PVC tubes, which are attached with staples or metal weights to the seabed in order to keep the grid in position.
In addition, the tubes have perforations that, when submerged, are filled with water, which means that they have negative buoyancy. The use of this grid helps divers to have better orientation during excavation, as poor visibility did not allow control or location of the survey.
Installation of the grid on the bottom where the underwater excavation is carried out
Teams of at least two divers carry out the excavation: an archaeologist who performs and supervises the excavation and a diver as support staff, in shifts of one hour in the background, who rotate to keep the excavation always active. They were developed in a systematic way to explore the potential of any archaeological remains.
Care should be taken with the removed sediment to prevent it from being re-introduced into the excavation; for this reason, equipment consisting of a metal head operator, a support diver to support the head hose and a support diver to support the exit hose should be required. At the bottom, work begins by taking photographs and removing vegetation. The suction head is positioned in the north corner and excavation of the contours of the grid begins.
Once the contour is defined, the sediment begins to be removed from the north to the south, leaving short spaces of time for the sediment to descend, seeking better clarity at the bottom.
Controlled underwater excavation process as seen from the surface
Depending on the context, the excavations end up being very shallow or deep, which complicates the position of the divers within the survey. The way to maneuver between the metal head, the output hose and the position of the divers is sought. All the elements located in the underwater archaeological excavation are duly recorded by in situ photography, which allows identifying their original context and certain characteristics that they present at the time of the discovery.
Controlled underwater excavation process
A record of the excavation profiles is also made, and measures are taken to establish the depth at which the elements are identified and to associate them later with the archaeological contexts (for example, if vessels are located, to know if they were inside or outside a vessel, or if any object belongs to the same cargo, etc.).
Once the underwater excavation is complete, the metal head and hoses are removed to clear the area and be able to make a photographic record of the background. It is worth mentioning that, due to the sea currents in the excavation area, the survey wells, no more than 1 m deep, are quickly covered again in a matter of hours, so there is no direct impact on the seafloor.
Diving conditions during underwater excavation
During underwater excavation, an emotion is generated that intensifies when visibility decreases, creating a unique sensory experience. The focus is on the close details, enhancing the texture of the seabed and the life that inhabits it. The sounds are amplified, transporting you to a mysterious and captivating underwater world. Adapting to these conditions requires skill and control, testing the skill of the underwater archaeologist.
Safety in this type of activity is paramount and requires the use of appropriate tools. Carrying a dive computer, such as the Shearwater Teric, provides crucial real-time information about depth and dive time. This device helps divers stay within safety limits and plan their excavations effectively. Constantly monitoring immersion information prevents incidents of decompression and other pressure-related risks. Therefore, the diving computer becomes an indispensable instrument for the safe and responsible practice of this work.
General view of the Nichupte lagoon, near the area where the underwater archaeological excavation was carried out
Results of the Underwater Excavation
In the excavations carried out in the Nichupté lagoon, near the shore, some natural elements could be identified at a very shallow depth (between 10 and 30 cm), such as roots, pastures, shells, among others. However, deepening the excavation, some contemporary elements were also found, such as glass bottle waste, cans, plastics.
The area near the excavation was explored and more elements were found that could correspond to some type of modern pier. Regarding pre-Hispanic archaeological material, ceramic fragments were found. The ceramic material has a red gibber and a polished surface finish to the outside, while inside it has no coating and the finish is smoothed, indicating that it could be a pot-shaped vessel; the paste is thin, with inorganic shells, light color, it has an average thickness between 0.6 and 1 cm, it has an oxidizing type cooking, it does not have decoration, the type of manufacture is modeled and it is a globular shaped piece body. These characteristics can be identified in materials from the late postclassic period (1200-1550 A.D.).
In this project, since no archaeological remains were found onsite in the Nichupté lagoon in Cancun, the construction of the bridge was authorized; however, thanks to the methodology used, the safety of the divers was maintained when carrying out a controlled underwater archaeological excavation.
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Gustavo García García holds a bachelor's degree in Archaeology from the University of Veracruz. He completed his thesis and he has worked on various archaeological projects in Mexico, including Archaeological Salvage programs. Since 2017, he has been a researcher in the Underwater Archaeology Department at the INAH. He is in charge of the Underwater Archaeological Salvage area, and his research interests include the analysis of archaeological materials, pre-Hispanic cultures, cave diving and the photogrammetric recording of underwater sites. He has several diving courses including the most recent SDI Sidemount course: PADI Open Water Diver // PADI Advanced Open Water Diver // PADI Rescue Diver // PADI Divemaster // RAID Cave 1 // GUE Drysuit Primer // GUE Fundamentals // Certificate by Nautical Archeology Society
