Cenote Dos Ojos

A few wooden steps take you into what looks like a swimming pool with a rock lid. The floor at the entry is pale sand, the water is an almost translucent blue, and for the first minute nothing about it reads as a cave. The dark starts at the edges, where the ceiling comes down to meet the water.

The Barbie Line goes first, and it is built as an introduction whether or not anyone calls it one. It runs out along the opening of the second eye, roughly 415 m of permanent line with daylight on it from end to end, and room to swim around big columns and stalactites and shafts of sun dropping through the large light galleries. Putting it first means you find out in the bright water how much faster buoyancy moves in fresh water than in the sea. Halfway along there is a plastic crocodile with a Barbie doll in its mouth. That is the name.

Then an hour on the surface, and the second dive is a different cenote's worth of atmosphere. The Bat Cave line heads west, about 300 m into much less light and a few metres deeper, through smaller chambers whose roof has never collapsed and whose formations are correspondingly better kept. The enclosure builds as you go. One diver reported that she could not always pick out the ambient light on that route even while on the permanent line, and said the honest thing about it: you can get to feeling a long way from the entrance.

The moment on that route is an ascent rather than a descent. The line passes an air filled dome and the guide signals the group up into it, and you stand in a chamber under the jungle with a live colony of bats on the limestone above you and the sound of them moving coming off the walls. Six minutes up there is a normal stay, about halfway through the dive. Then back through the darker sections to the steps, with mirror effects on the ceilings on the way.

Almost nowhere else on this coast gives you two genuinely different dives without packing the car between them. Every other classic pairing means diving one cenote, loading up and driving to the next. Here the second dive starts from the same steps as the first, and divers say so unprompted days after doing it: no drive between dives makes it easy. The contrast between the two lines is not a marketing distinction either. One is wide, bright and long sighted; the other is dark, tighter and ends inside a chamber of bats, and people who dive both usually name the second as the better of them.

The other thing worth knowing is the crowd. Dos Ojos is one of the six most visited cenotes in Tulum municipality, it is formally graded as a site tourism has already altered, and none of the busiest cenotes here has a carrying capacity study behind it.1 Divers describe queues of lights on the line and hovering motionless while nothing ahead moves. What saves the dive is that the pressure is concentrated rather than constant: arrive at opening and the cavern can be yours, and the snorkellers who fill the surface all day are never on the line with you.

Cave divers opened this system through the two sinkholes in 1987, or close enough that the late 1980s is the safer date, and they have not finished yet. For three decades the cave behind them was called Sistema Dos Ojos and sat among the longest surveyed underwater caves in the world. A dry connection to Sistema Sac Actun turned up in August 2012 and an underwater one in January 2018, and by survey convention the smaller system took the larger one's name and stopped existing. Sac Actun now measures 379,569 m of surveyed galleries and the name Dos Ojos belongs to no cave system at all,2 so any kilometre figure still published under the old name describes a particular year rather than the water as it is now.

Some of those years reached cinemas. Journey into Amazing Caves, the highest grossing giant screen documentary of 2001, followed two cavers through the ice caves of Greenland, the underwater caves of the Yucatán and the earth caves of the Little Grand Canyon.3 The Yucatán footage is generally placed in this system, and parts of The Cave in 2005 and of Planet Earth in 2006 were shot here too. On 3 November 2010 the Venezuelan freediver Carlos Coste swam 150 m through the cavern on a single breath in 2 minutes 32 seconds, the first time a freediving record was attempted inside underwater caves.4

The park came last. The Ejido Jacinto Pat, which holds this land communally, consolidated its cenotes into Parque Dos Ojos in the mid 2010s with a ticket office, a road and a museum of the ice age built around what the cenotes preserve of the evolution of species.5 In high season the park takes around 300 people a day, and only a small share of them are divers.

The order of the two dives is a prerequisite rather than a convention. The Barbie Line is graded Level 1 on the regional register and the Bat Cave line Level 2, and Level 2 asks for a Level 1 cenote dive already logged.6 The morning dive is what qualifies you for the afternoon one, which is why every operator runs them that way round, and why an Open Water diver arriving with no cenote history can still dive both routes here in a single day.

The guide is not optional either, and the reason is a landowner's gate rather than a statute. The federal standard binding Mexican dive operators grades maximum depth by certification and never once mentions a cave or a cavern; one of its clauses even lets an advanced diver waive supervision in writing.7 The authority here is the Ejido Jacinto Pat, which owns the ground, working to the standard CREER publishes: four divers to a guide, minimum age 15, a permanent line on both routes, and nothing entering the water after 15:00.

Then the money, and the question most visitors get wrong. Diving costs 400 pesos, handed over at the Parque Dos Ojos ticket counter, but it is priced against the cenote rather than against the park. The same counter charges 700 for The Pit and Dos Ojos together, and entry to a park cannot cost more because you visited a second cenote inside it. Snorkelling is 350 or 400 depending on who quotes it, a camera adds about 300, and none of it takes a card. Ask whether your operator's price includes the gate fee, because that one difference explains most of the spread between quotes.

The gate opens at 08:00, closes at 17:00 and posts a last entry of 15:00, the same cut off the regional standard sets for starting any cenote dive. Divers who get in before 09:00 repeatedly have the water to themselves, and an afternoon slot works from the other end. The 5 mm rental suit is not overkill at 25 C once you have done two dives with an hour of standing around in between. And leave the repellent and the sunscreen in the car, including anything sold as biodegradable or reef safe: turn up wearing it and you can be sent for a shower before you are allowed in.