Swiss lakes are world-renowned for their rich archaeological heritage from the time of the pile dwellings, when Neolithic to Bronze Age people built their villages on the shores of alpine lakes.

For the thousands of years that followed, people used Swiss lakes as trade routes. A precious aid for transporting goods, especially heavy or large objects. Blocks of stone extracted from the Jura quarries would have been difficult to carry on roads. Whether during the Gallo-Roman period, the Middle Ages, or the late periods, many ships did not reach their destination and sank to be quickly forgotten, buried under the sediments.

Ever changing lakes

In the 19th and 20th centuries, the Three Lakes region underwent profound changes (construction of reservoirs, canals, etc.) to stabilize water levels during floods or droughts. This constraint imposed on the lakes resulted in the reshaping of their beds, much like a diverted river. This erosion primarily affects coastal areas, with significant sand shifts, bringing to light archaeological remains such as Neolithic dugout canoes and 19th-century barges. A fragile catalogue of forgotten witnesses to our history.

Our recent underwater excavation project focuses on several shipwrecks which, due to their age and state of preservation, are invaluable sources for understanding the evolution of naval architecture and navigation in the Three Lakes region of Switzerland.

These remains were discovered during aerial prospecting flights. Fabien Langenegger, archaeologist at the office of heritage and archeology of the canton of Neuchâtel (OARC), is responsible for monitoring local underwater heritage. For many years, he has collaborated with the balloonist and engineer Fabien Droz to monitor the erosion fronts that endanger the prehistoric pile dwellings, but also to prospect the 30 kilometers of coastline the canton of Neuchâtel enjoys.

Wood has a voice

An anomaly spotted in 2015 allowed the discovery of a Gallo-Roman barge that is about two thousand years old. In 2017, a pile of large stone blocks led to the discovery of a second wreck, dated precisely to 1776 thanks to dendrochronology (a scientific method allowing the dating of pieces of wood by counting and measuring the tree rings). A third wreckage, which appears to have been intentionally sunk in the 16th century as the basis for building a signal, completes this trio of outstanding vestiges.

The rare barges that have been found in our lakes have almost all sunk with their cargo of limestone blocks, creating reliefs visible from the air. These boulders also helped stabilize the remains of the wreckage by keeping it at the bottom until silted up.

High scientific stakes

To date, only three Gallo-Roman wrecks have been identified and studied in Switzerland. In addition to the one discovered in the bay of Bevaix (NE) and presented in the navigation room of the Laténium Museum, a boat and a barge were excavated in Yverdon-les-Bains (VD) visible at the Yverdon Museum.

The wrecks recently discovered by Fabien Langenegger could prove to be historically important.

In the region of Trois-Lacs and Léman, there is a 1700-year gap to fill, between Roman boats dating from the 2nd century AD. and the many 19th century boats that were found. The study of the remains of the 16th and 18th century boats may therefore be paramount to better understanding the evolution of shipbuilding on our lakes.

Short-term threats

Located at a shallow depth and protected by a thin layer of sediment, the three wrecks are now vulnerable, as they are located in a part of the lake particularly exposed to the prevailing winds.

For this second project to study and preserve lake heritage, the Octopus Foundation will provide a team of five qualified divers and two pilots of aerial and underwater drones. The foundation thus supports the collection of scientific data and informs the public about the objects of study. In exchange, the OARC allows the Octopus Foundation to acquire expertise in underwater archaeological excavation techniques in cold water and to publicize the excavation on its own behalf and on behalf of the OARC.

The second campaign took place in October 2019. It led to the excavation of a unique assemblage consisting of an extremely well-preserved 16th-century wooden barge and a stone structure in open water with a quadrangular base. According to initial investigations, this structure served to mark the entrance to the old Thielle Canal, which led to Lake Biel.

Thanks to underwater 3D modeling, the objective is to keep a record of each stage of the underwater excavations.

The Octopus Foundation was easily convinced by the idea of collaborating on inland water issues, particularly for the study and preservation of shipwrecks threatened by underwater erosion.

In November 2018, a scouting mission brought together Fabien Langenegger and the Octopus Foundation diving team to collect all the data necessary for the preparation of the project. During this short three-day mission, it was also possible to dive on the wreck of the Quai Osterwald in Neuchâtel. This ship, which sank in 1853, is 30 meters long and lies between seven and eight meters deep. In one dive, the team was able to deploy the underwater markup and make a photogrammetric acquisition of nearly 600 photos. The 3D model of this magnificent wreck is available here.

Aerial drones

The use of aerial drones is particularly useful for detecting underwater objects when they are at shallow depth and in clear water.

By flying several tens of meters above the surface, the pilot may spot the wrecks and pin them on a map. The drone can thus scan certain areas which will then have to be excavated by the underwater archaeologists.

For this project, the use of several drones with different optics will help archaeologists collect valuable data on these wrecks.

Underwater drone (ROV)

Using the OpenRov Trident may help us to:
– preview a wreck before sending a team of divers
– perform photogrammetry and 3D modeling of submerged sites
– capture images at depths and in areas difficult to access by divers

3D models of wrecks

Once the underwater photographic acquisition has been completed, the Octopus Foundation processes the data to obtain a 3D modeled area like the ones below.

By clicking on the symbol in the center of the window, once the model is loaded, you can rotate the area by clicking in the center and moving the cursor. You can also zoom and move the model by holding down the shift key.

These simple and free tools provided by the Octopus Foundation allow people with little or no diving experience to explore the depths of the lakes and seas, and study various archaeological pieces with no risk of damage.

Photogrammetry

Whether for the public or diving enthusiasts, these digital models are effective visualization tools. But are they also useful for scientists? We keep in mind that one of the first objectives of the Octopus Foundation is to support research and scientific exploration of the oceans.

From the digital 3D model, a simple visualization element, the computer program makes it possible to extract a scientific tool: the orthophotoplan. By a vertical projection of the entire relief on a horizontal plane, this centimeter-accurate map respects all dimensions on the ground. While diving time is limited by the air contained in a tank, it is now possible to extract the archeological site out of the water to allow it to be studied carefully on land.

The 16th-century barge

This second mission in Lake Neuchâtel, focusing on the 16th-century shipwreck, was conducted from September 30 to October 14, 2019, with a team of four divers and a drone pilot.

Located today at a depth of 1.8 meters, this wreck was originally visible only as a pile of stones of varying sizes and shapes, roughly arranged along a north-south axis.

While searching through archives, archaeologist Fabien Langenegger discovered a 17th-century map (Schauenbourg Collection in Bern) depicting a stone marker erected on a shoal to indicate the entrance to the Thielle Canal, which connects to Lake Biel. This marker was apparently topped by a wooden mast with a flying flag. This navigational landmark was particularly useful during high water to prevent boatmen from running aground in the vast marshy areas.

Furthermore, it is handwritten on the map in Old German, right next to this marker: “Grosser Stein, darinn ein panerstock vor Zeiten gesanden” (“Large stone, on which a pillar of jurisdiction had long stood”). This would mean that this marker, in addition to serving as a guide for sailors, must also have served as a border beacon between the County of Neuchâtel and the Canton of Bern. The Thielle Canal still forms the border between the two cantons today.

To support the connection made between this 17th-century map and the stonework, evidence was found during underwater dives. In 2016, while excavating around the blocks, pieces of wood were discovered, revealing the presence of a boat buried entirely under the sand and partially located beneath the stone structure.

During the underwater excavations, we completely uncovered the wooden boat, measuring 15 meters long and 3.5 meters wide. It became clear that the stones could not have been the boat’s cargo. Typically, on barges, the loads of limestone blocks were arranged in two rows along the long sides of the boat, leaving a passage in the middle for the sailors. Here, the arrangement of the stones suggests an unusual method of construction in open water, already known in Roman times. The base of the structure is built on land on a boat, which is then towed and sunk precisely in the desired location, with the construction completed by adding stones as it is lowered into the water.

Furthermore, a dendrochronological analysis of the fir planks gives this wreck a terminus post quem of 1537. This means that the ship would have been built in the years 1537-1540 to be used as a transport ship for about 80 years, before being used one last time for the construction of the signal around 1620-1625 during the Thirty Years’ War, opposing Catholic forces to those of the Protestants.

During the excavations in October 2019, several objects were discovered, including a glass flask, a coin (a Batz from the County of Neuchâtel dated 1622), military jacket buttons, a leather shoe with a wooden sole, and fishing weights. These items, starting with the Batz and the military uniform buttons, help to clarify when and why this beacon was most likely built.

In 1618, the Thirty Years’ War broke out, primarily between the Catholic forces of Charles V (Spain, Holy Roman Empire) and Protestant German princes who rose up in revolt. To quell the rebellion, Charles V launched his vast army from Spain into what is now Germany. In 1624, this army crossed Franche-Comté, west of the Jura Mountains. The Protestant County of Neuchâtel feared being pillaged by the large Catholic army. The Neuchâtel authorities then decreed a general mobilization and the first defenses of the small state, establishing guard posts along all its borders. These were primarily along the Jura Mountains, but also along its borders with neighboring cantons, including Bern. The Neuchâtel archives of the time specify that a guard post, manned by 100 soldiers, was established “at the mouth of the Thielle Canal.” It is therefore possible that as part of this defense of the County in 1624, the soldiers were ordered to physically mark the border with Bern, even in the waters of the lake.

From September 30 to October 14, 2019, the Octopus Foundation team provided support to archaeologist Fabien Langenegger at OARC. No less than 11 divers worked tirelessly to remove the sand and then study a 16th century wreck in Lake Neuchâtel (Switzerland).