Kategorie: News
A four-kilometre walk through the jungle – a new chapter for Sac Actun
A four-kilometre walk through dense jungle, then down into narrow, flooded passages: this is how an expedition began that is attracting attention in the cave world of Quintana Roo, Mexico.
An exploration team from the Instituto USAH has linked the previously separate O’Ho Tucha cave system to the vast Sistema Sac Actun. The discovery was announced on 6 November. This adds around two kilometres of newly documented passages to the overall system.
A long way to the entrance
The starting point was the recently discovered cenote Aktun Kalom Kin. The explorers only reached it after a walk of around four kilometres through the forest near Tulum. Underwater, a labyrinth of narrow passages awaited them, which, according to reports, extends in a south-westerly direction towards Tulum.
The team made progress in two stages. First, they succeeded in connecting O’Ho Tucha with the eastern section of Aktun Kalom Kin. The divers then explored the western section and finally confirmed the connection to Sac Actun.
Following the naming conventions customary in cave exploration, when such a connection is made, the smaller system is assigned to the larger one. O’Ho Tucha had previously been documented as a separate system: in March 2018, as part of the Vanilla Sky Project and the Gran Acuífero Maya, around 5.97 kilometres were surveyed and reported to the Quintana Roo Speleological Survey. It is now part of Sac Actun.
How big is Sac Actun now?
According to the most recently published survey data from December 2024, Sac Actun comprises 379.569 kilometres of documented passages. If O’Ho Tucha and the approximately two newly reported kilometres are added, this results in a calculated total length of around 387.5 kilometres.
However, this figure is provisional and has not yet been officially confirmed. The actual length of the system depends on how the survey data is collated, whether sections overlap, and what new discoveries have been made in the meantime.
Not the first connection of this kind
Sac Actun has grown through connections. Nohoch Nah Chich was integrated as early as 2007, and other systems such as Aktun Hu were added later. The connection with Dos Ojos, established by the Gran Acuífero Maya under the leadership of Robert “Robbie” Schmittner, attracted worldwide attention in January 2018. At that time, a contiguous system of around 347 kilometres was formed. Dos Ojos retains its name as a cave area but is part of Sac Actun. The latest discovery, O’Ho Tucha, follows the same principle.
More than just extra kilometres
The underwater caves of the Riviera Maya are the accessible sections of a vast karst aquifer. It is crucial for the water supply, biodiversity and ecological stability of the Yucatán Peninsula. Every newly documented connection improves our understanding of this underground structure.
However, a diveable connection does not automatically mean that the waterways are fully understood. The actual flow directions and transport pathways can only be confirmed through further investigations: flow measurements, tracer experiments, water analyses and long-term monitoring.
Such findings are particularly important in the area around Tulum. Tourism is growing rapidly and the town is expanding. Pollutants can spread via the underground waterways and endanger ecosystems far away.
Just how extensive is the network really?
The new connection highlights just how patchy our knowledge of the Yucatán’s cave systems remains, even today. Systems that appear separate on maps may in reality be only a few metres apart. Conversely, a hydrological connection does not necessarily mean that there is a passage that can be dived through from end to end.
The explorers from the Instituto USAH point to other cave systems in the area where potential connections have not yet been documented. The scientific project MAYAS (www.projectmayas.com) is also investigating the hypothesis that Sac Actun, Ox Bel Ha and other systems could form part of an even larger regional groundwater network. No such overarching connection has yet been proven.
Exploration continues
The connection between O’Ho Tucha and Sac Actun shows that even in one of the most intensively explored underwater cave regions on Earth, fundamental discoveries are still possible. With every new expedition, the picture of the hidden landscape beneath the rainforest of Tulum becomes clearer.
For it is not the caves that change, but our understanding of how they are interconnected.
Further information and sources:
Concept, images and idea by Dirk Penzel (Diving Cenote)
Instituto USAH, press release/map on the connection between O’Ho Tucha and Sac Actun, 6 November 2026 (via Noticaribe: Conectan nuevas galerías al gigantesco sistema subterráneo Sac Aktun en Tulum – in English: New galleries connected to the gigantic Sac Aktun underground system in Tulum)
La Revista Peninsular: Exploradores conectan los sistemas de cuevas O’Ho Tucha y Sac Aktún en Tulum (in English: Explorers connect the O’Ho Tucha and Sac Aktún cave systems in Tulum)
Scintilena: Sac Actun si estende verso Tulum: O’ho Tucha entra nel sistema attraverso un nuovo cenote (in English: Sac Actun extends towards Tulum: O’ho Tucha enters the system via a new cenote)
Wikipedia: Sistema Sac Actun (history of connections)
Project MAYAS (Robbie Schmittner Expeditions): Scientific expedition project on groundwater movement on the Yucatán Peninsula