YUCATAN PENINSULA, MEXICO – In the shadows of a full moon night, a giant sea turtle laboriously drags his domed body across the sugary sand towards the water’s edge.

From a distance, I follow the mighty creature’s slow march toward the sea until the behemoth slips beneath the surf and I’m left standing alone on Akumal Beach — which in the Mayan language means “Place of the Turtles.”

This is my second visit to Akumal. My first time here in 2008, I followed a turtle — maybe the same one? — into the Caribbean and became so fascinated with its undersea world that I enrolled in a diving course.

Four years later, I return as the proud holder of a rescue diver certificate, one step away from being recognized as a professional diver.

Since my last visit here, I’ve logged more than 60 dives in exotic locations like Nice, France, Cuba, Hawaii, the Philippines and Hong Kong.

But my heart remained in Akumal.

On my last visit, I promised myself that one day I’d return here and be good enough to make a dive into the legendary underwater cenotes, huge caves or sink-holes that may have been created 65 million years ago when the Chicxulub meteorite fell from the sky and impacted this area of Mexico.

That day has finally come.

Left: Diver Karen Wang stands out in the darkness of Mexico’s cenotes. Right: Karen was lured to diving by Mexico’s giant turtles.

“Hurry,” says Saul, my dive instructor who will lead me and a few other excited divers into the Dos Ojos underwater cenote — one of the most fabled of the caves, and one which has deep roots in Mayan culture.

“We have to finish our dive by 5 p.m.,” says Saul.

“Why?” I wonder aloud.

“All cenote dives must finish by 5 p.m. because the Mayans believe water spirits come out after 5 p.m. So we must respect that tradition and leave the cenotes to the spirits.”

The Mayans believed underwater cenotes were the gateway to the afterlife and subsequently made many sacrificial offerings — some human — in the sink-holes.

During our dive, we come across some bones but before the dive Saul reminds us to be respectful — “don’t try and pick the bones up,” he tells us.

Maya history suggests the “Rain God Chaac” lives in Dos Ojos, which contains the deepest of all cave passages, dropping 119.1 metres from Dos Ojos.

In the Caste War of the 19th century, during which the Maya people fought against the authority of the Mexican government, some cenote caves were used as hideouts.

Later, those caves became gathering places for social interaction and legend has it the first jipijapa, or Panama Hats, were made in those caves.

Dos Ojos, which means “Two Eyes,” was first explored in 1987 — when exploration of the underwater cenotes first began in earnest.

The cave system stretches an amazing 82 kilometres and features 28 known entrances.

Left: The giant sea turtles attract a lot of attention in the giant sink holes. Right: The cenotes can be dangerous places in which to swim.

Adrenaline rushes through my veins as we drive through thick jungle to Dos Ojos. We lumber down a hillside and struggle with our dive gear — I’m also weighted down with two huge cameras — before we reach the entrance of the fabled cenote.

We check our dive computers before jumping one-by-one into the yawning entrance of the cave.

It’s already 4 p.m. — we have less than an hour to explore Dos Ojos.

Saul expertly guides us through the narrow openings of the cenote, which is shrouded in darkness. It’s so pitch black at points that I can’t even see a hand in front of my face.

It’s a frightening experience, even for a seasoned diver.

I reach to check my air pressure gauge but can’t find it. Now I’m nervous.

I thought the night dive I recently completed in Hawaii was the ultimate scary experience underwater. This cenote dive beats that by a mile on the fear metre.

As I swim further into the cenote, I’m struck by how cold the water is — much colder than what I experienced on Akumal Beach and the Caribbean Sea.

When I’m caged by the stalactites that have formed over time in the cave, I suddenly experience claustrophobia for the first time in my life.

Where is Saul?

As I gingerly move forward, I suddenly feel a tapping on my tank.

At first, I think a fish has bumped into me. But fish are soft and the tapping sounds like human fingernails hitting the metal tank.

Tap. Tap. Tap.

The sound is coming in patterns now. I’m really scared!

Tap. Tap. Tap.

Just as I’m about to enter into full blown panic mode, Saul appears. I’m safe!

The instructor taps his finger against his watch and points to the surface — my cenote dive is over. Thank God, I think to myself as we slowly swim back to the entrance.

It’s just a few minutes before 5 p.m. when we crawl out of the cenote.

“The spirits will be happy — we finished the dive before 5,” says Saul as we get out of our gear.

On our way back to the hotel, I relate the tapping incident to Saul and the others.

“Did the tapping start at the place in the cenote where we met?” asks Saul.

When I tell him yes, he smiles and suggests maybe the Rain God Chaac “was having some fun with you.”

The cenote spirits certainly lifted my spirits on this day.