The sump pool of Sump 1 in the Rio Uluopan. Photo by Adam Haydock.
The last exploration in the Río Uluapan happened in 1995 when Bill Farr, on his final dive, surfaced on the far side of Sump 1, looking at a 14 metre tall water fall pouring all the water flowing through this cave system into the sump pool. Bill then turned and went back, and since that time nobody else has continued exploration in this amazing cave.
After our epic 8-week long trip to the Cueva de la Peña Colorada, where we hit an impenetrable rock pile in Sump 7 only 20 metres from the previous end of exploration, and then got flooded in, our team was ready for a bit of change. We therefore decided to focus on the Cerro Rabon, in particular the Río Uluapan resurgence, for a while. Hence we spent April of 2019, with a team of 9 strong cavers and cave divers, at the Uluapan resurgence.
After several dives we finally found the water fall chamber which Bill Farr got to in 1995, which, given the passage dimensions of this cave of up to 40 metres x 20 metres, and the light sources which were available at the time, was quiet an impressive feat. We rigged handlines up the water fall, and soon after found Sump 2 not far beyond. After setting up several tyroleans between the sumps to transport our dive gear across very sharp rock, we finally got to do the first dives in Sump 2.
Since it is not known where the water emerging at the Río Uluapan resurgence comes from, we had no clues on what the cave would do. We could have dived Sump 1 to find that the cave immediately headed up vertically, which would have resulted in us aid climbing a lot rather than spending much time underwater, or we could have found many small sumps, but we we did find was what must be one of the most amazing sumps on this planet. It starts huge, goes quickly down to ta depth of 70 metres, heads back up to shallower waters, back down to 60 metres, back up, and then heads down to over 100 metres depth where we turned.
It is hard to properly describe the dives we did in those two sumps. With a visibility of ~15 metres it was often not possible to see all walls of the cave, and all our efforts to video the sumps turned out average because the cave ate all the 50,000 Lumens we threw at it for breakfast. Luckily we were using powerful scooters to fly through the sumps to avoid much unnecessary decompression time in Sump 2. Nevertheless, with the current end of exploration being about one kilometre into Sump 2, at a depth of 100 metres, going deeper, next year will be great a challenge.