Pollasillagh Sump

Pollasillagh Downstream Dive Report:

Diver: Nathaniel Laplaud

Sherpa: Raymond Bell

Date: 18 Oct 2026

Entered via Pollasillagh having rigged a ladder for descent. The new bar is an improvement on the new rigging setup. Dropped the bags at the ducks and headed upstream to sight a potential dive site in Mastadon Upstream. Very promising site and worth a visit. Good water flow coming out of the sump.

We then returned and set into the exciting dive base of Downstream only to be dissapointed by the <1m depth in the big rift. Passing through the 2 ducks as reported in 1971. Exiting the water I had to remove the dive equipment to passa a tight dry squeeze before I arrived at the 2nd pool with the sump positioned river left of the pool. I descended feet first, very excited that it may open up into the deep water Expected in the connection with John Thomas, which lies at -19.1m presently. However this passage is not found yet as I bottomed at -2.5m in a boulder choke. I tried 3 different potentials to continue downstream, only one proving somewhat promising as it rose to a surface, however the airspace was too low to fit my head into. Returning I progressed upstream within the boulder choke to see if an alternative terminus could be located further west in the cave, however ran out of line and belayed onsite. Not much digging prospects. The second pool is blocked by a mud choke and mostly large boulders comprise the underwater portion of the choke. Time to find this choke in Upstream of John Thomas.

The passage proportions are vastly different here compared to at depth in John Thomas. John Thomas being some 7m wide just under and this choke being maybe 4m wide. Not very spacious. Ray identified some other potential dive leads while waiting, and a curious inlet!