Hidden deep in the jungles of Mexico’s Yucatán Peninsula lies one of nature’s most surreal wonders: an underwater river flowing beneath the sea. Known as Cenote Angelita (meaning “Little Angel”), this incredible phenomenon attracts adventurous scuba divers from around the world. But is it really a river? Let’s dive into the facts behind this optical illusion that’s often called the “river under the ocean.”
What Causes the Underwater River Effect?
Cenote Angelita is a deep sinkhole (cenote) formed by the collapse of limestone bedrock, exposing groundwater below. The Yucatán Peninsula is dotted with thousands of these cenotes, many considered sacred by the ancient Maya.
What makes Angelita unique is a natural phenomenon called a halocline – the sharp boundary between layers of water with different salinities:
- The top layer (down to about 29-30 meters) is fresh water from rainfall.
- At around 30 meters, a thick, misty cloud of hydrogen sulfide (H₂S) forms a 1-meter layer. This gas, produced by decomposing organic matter in low-oxygen conditions, is denser and creates a foggy barrier.
- Below this, saltwater fills the deeper parts of the cenote (up to 60 meters or more).
The hydrogen sulfide layer, combined with fallen leaves, branches, and debris along the edges, creates the stunning illusion of a flowing river complete with “banks” and even a small “island” in the middle.
Divers describe swimming through the cloud as entering an eerie, otherworldly forest – with tree trunks protruding from the “riverbed” and visibility shifting dramatically.
Diving in Cenote Angelita
Located about 17 km south of Tulum in Quintana Roo, this advanced dive site requires certification and experience (often at least 20 logged dives) due to its depth and cave-like conditions. The hydrogen sulfide layer can be disorienting, and the dive feels like exploring a mystical underwater landscape.
Photographers like Anatoly Beloshchin have captured iconic images that went viral, showing divers “floating” above what looks like a misty river on the seafloor.
Why It Goes Viral
This natural wonder perfectly blends science and magic, making it a favorite for travel blogs, documentaries, and social media. It’s a reminder of how diverse and breathtaking our planet’s hidden spots can be.
