We start our week with a dive on our most promising, and challenging, target, a cenote not far from a site we dove on our previous expedition that contained carved glyphs, ceremonial objects, and evidence of human sacrifice. But where that site was accessible by an easy walk into a shallow basin, Treehole II* is literally a hole in the ground at the base of a large tree--and a 40-foot drop to the water.

*(to deter looters, ARCHAEOLOGY will not reveal the real names and exact locations of most archaeological sites visited on the expedition)

Our only practical means of access at the time is a jerry-rigged system of two extension ladders tied to one another and suspended from the base of the tree. At least the tree's roots extend all the way to the water and provide some stability to keep the ladder from swaying wildly as we descend.

Patrick inches onto the ladder. Equipment will be lowered into the cenote after all the divers are down. (Alisa French)

One by one, our first shift of seven divers, clad only in wetsuits and masks, creeps down the ladders. Noone even bothers to reflect on the craziness of the climb, however, once we're bobbing in the circle of sunlight that streams from the hole in the jungle floor some four stories above. Ooohs! and aaahs! echo off the damp walls of the enormous cavern, dislodging a few irritated bats. The water at the surface is warm and crystal clear and we can already spot several intact pots and human bones resting on the debris pile about 20 feet beneath us.

Next comes the equipment, lowered by rope: still cameras, video cameras, and personal gear, ranging from standard single-tank recreational setups to technical double-tank cave diving configurations with reels and large halogen lights. All of the very heavy and fragile equipment has to be wrestled into and wrestled with in the water. If anything has gone awry in the trip down, from a fritzed o-ring to a banged-up lighthead, it has to be hoisted back aboveground, repaired, and returned, adding frustrating minutes of wait time.

While we finish gearing up, Memo makes a quick dive and lays a line into the deepest part of the cenote. The line will help us find our way back to the ladder in case the visibility gets bad. He resurfaces a few minutes later and briefs us on what to expect: most of the Treehole II cenote lies within the open cavern area, which means there's no overhead obstruction to prevent us from surfacing in case of an emergency. About a hundred feet east and in a little dogleg to the left, the cenote hits its maximum depth at 120 feet.

It's been over an hour now since we put the ladder down and even the bats seem wound up and ready to go, chattering and trolling low over the water. The plan: fan out and swim out along the left side of the debris pile towards the max depth point, then circle back around the pile clockwise.

"Everyone ready?" Memo looks around, then gives his wrist-mounted dive computer an painfully long final glance. Then a big smile and a thumbs down, the universal dive signal for descent.

Treehole II may be an enormous cavern, but since the only sunlight comes from the tiny hole we entered through, it's like diving in the dark. This video, shot for the most part in Treehole II by James, gives you an idea of the conditions. (Click here for video.)

The skull of an older woman found in Treehole II exhibits the cranial deformation performed by the Maya from the Preclassic to the Postclassic periods. A study at the Universidad Autónoma de Yucatán revealed that approximately 90 percent of the Maya population had their heads artifically shaped in early childhood. For more on the study, click here. (Patrick Dickson)

In spite of the conditions, with two shifts of divers and over two hours of total dive time, we have enough sets of lights and eyes to make a pretty comprehensive initial sweep of the cenote. Treehole II contains the remains of at least four people: one adult with its vertebrae still articulated in a neat line on the cenote floor; the intact skull of an older woman, two crushed skulls, and seven thigh bones. We also found a large amount of broken ceramics and some beautiful intact vessels, which appear to date from the Classic period (A.D. 250-900).

As wonderful as it would be to raise the vessels and inspect them aboveground, it's out of the question. Memo's explorations of the cenotes in Yucatán State are considered nonrecovery surveys--that is, absolutely nothing is touched or moved, and everything discovered on the dive is recorded in a report that he later submits to the state offices of the Instituto Nacional de Antropología e Historia (INAH), Mexico's federal anthropology and history institute.

Particularly since nothing can be touched or examined underwater--even fanning sediment off of an artifact is a no-no--the first thing everyone does once they surface and pull the regulator out of their mouth is ask a question:

"Was that a cranium frag or ceramic over by the jawbone?"
"Who else saw that gorgeous plate wedged in the crevice at ninety feet?"
"Is that a little cave entrance way in the back by the big boulders?"
"I counted three skulls. Did anyone else count more?"

The quality of ceramics and initial number of bodies we identified certainly seems to suggest that Treehole II was a sacrificial site at some point in history; if the ceramics are indeed Classic period, it would tie in with the artifacts we found in the nearby cenote on our previous expedition. The big question is whether everything we found was thrown in from that small hole on the surface, where it drifted and/or rolled up to a good 60-80 feet where we eventually found it, or whether the ancient Maya actually jerry-rigged their own questionable ladder and descended into this cavern to make their offerings in more precise locations. Did the ancient Maya also climb down into Treehole II to make their offerings? All we know is that we just had an exciting dive, and discovered some great artifacts. Now, if we can get out of this hole in one piece, our expedition will be off to a great start.

[Larger Image] (Melisa French)