The Underwater Exploration Group of the Great Mayan Aquifer Project connected two of the largest flooded cave systems in the world on January 10.

The discovery comes after a 10-month long exploration of the cave systems known as Sac Actun and Dos Ojos located in Quintana Roo, Mexico, making it the largest flooded cave in the world.

In a video posted on GAM’s official YouTube page, the group of researchers can be seen exploring the hundreds of kilometers of passages. As of writing, the video has over 80,000 views on YouTube. Credit: The Great Mayan Aquifer Project via Storyful