After 10 months of work, researchers in Mexico have discovered the world's longest underwater cave.

The Underwater Exploration Group of the Great Maya Aquifer Project (GAM) found a connection between two of the world's largest flooded cave systems — Sac Actun and Dos Ojos — located in the Yucatán Peninsula. At 215.6 miles, the linked systems now form the longest known flooded cave.

"This immense cave represents the most important submerged archaeological site in the world, as it has more than a hundred archaeological contexts. Along this system, we had documented evidence of the first settlers of America, as well as extinct fauna and, of course, the Mayan culture," said Guillermo de Anda, researcher at the National Institute of Anthropology and History and GAM director, in a statement.

In this video, shot by Brian Wiederspan/Jeanna Edgerton (GAM)/@proyectogam, divers explore the cave system:

Although this phase of the project began in March 2017, GAM director of exploration Robert Schmittner had been searching for this connection for 14 years, gradually mapping new tunnels and galleries as he found them.

Before this, the Ox Bel Ha System was the longest at nearly 168 miles; the Sac Actun System was second at 163 miles. Third is the KooX Baal System at 58 miles and fourth is the Dos Ojos System, with 52 miles. This last one is now part of the Sac Actun System.

According to caving rules, when two systems are connected, the largest cave absorbs the smallest and the name of the latter disappears.

The finding is also valuable because the cave supports wide biodiversity due to all the fresh water. According to the statement, "This aquifer, had given life to this region of the Yucatan Peninsula, from ancestral times, to the present day."

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.