The cenotes of Yucatán are known all over the world for their clear water and their incredible underground landscapes.
One of the most surprising phenomena found there is the halocline, a zone where fresh water and salt water mix, creating a blurred effect and distorted light.
Before diving there, it is important to understand this phenomenon. Without preparation it can be disorienting, but with a little knowledge it makes the dive even more impressive.
What is the Halocline ? The science behind this phenomenon
The halocline is a zone in the water where two layers with different salinities meet, fresh water coming from rain and underground rivers and salt water coming from the sea.
This phenomenon is explained by density. Salt water, being heavier, stays below while fresh water floats above. When a diver crosses the halocline, the light is distorted and visibility becomes blurry.
How to recognize a halocline ?
Visually, crossing a halocline gives the impression of diving into a mirage.
The water becomes blurry and everything looks hazy, like a thick fog. Some divers describe the sensation as floating inside the water or witnessing a surreal scene where shapes and colors ripple.
Visibility suddenly drops, sometimes making it difficult to see your buddy or the nearby environment. This moment can unsettle an unprepared diver, but it becomes fascinating when you know what to expect.
How do haloclines form in cenotes ?
Cenotes are natural sinkholes created by the collapse of limestone in the Yucatán Peninsula. Connected to a vast network of underground rivers, they are filled with fresh water coming from rainfall and infiltration.
Beneath this layer, salt water from the Caribbean Sea seeps in through cavities and underground passages. Being denser, it stays at the bottom while the fresh water remains above.
This superposition creates a natural stratification, a visible boundary between the two layers called a halocline.
Top 3 cenotes to see haloclines
Diving in a cenote is already a unique experience. But crossing a halocline, where fresh water meets salt water, adds an almost magical dimension to the adventure.
Here are three must see cenotes in Yucatán where you can experience this impressive phenomenon.
Cenote Chac Mool
Highly appreciated by divers, Chac Mool is famous for its haloclines that can be seen from just ten meters deep.
They create spectacular mirage effects, enhanced by the play of light coming from the openings in the ceiling.
Cenote The Pit
A deep and majestic cenote, famous for its spectacular descents. The halocline there is very pronounced and creates a striking mirage effect.
Combined with the rays of light that pass through the opening and reach the depths, the experience becomes almost unreal.
Cenote Angelita
A unique cenote, famous for its mysterious underwater river. At about thirty meters deep, a thick layer of hydrogen sulfide separates the fresh water from the salt water and creates a spectacular halocline.
The effect is striking. It feels like flying above a dark cloud, as if two distinct worlds existed in the same place.