John Thomas Cave & Sump

Club Trip Report

30th May 2026

John Thomas

Nat, Ray, Mark, Bryan, Dorothy, Conall, José, James

Aim to visit sump and put Nat the diver into the water.

10m handline, 10m traverse line, x2 12l cylinders. Drysuit under oversuit.

Excellent Trip thank you to all for your immense help! Really exciting progress made.

Callout taken by Irish Cave Divers. Everyone in the group had a tackle bag to carry each over the fields and into the cave.

The cave starts with a low horizontal crawl, challenging for bringing bags through and great teamwork was utilised to progress the gear through.

Ray rigged the handline and Nat and Dorothy worked together to lower the bags and bottles down to Ray through the rift. Each bottle weights 14.5kg plus about 3kg of compressed gas which is quite the workout and heavy lifting.

A traverse line was used to cross the rift protecting us from slipping in the already developing muddy environment. And a second handline usage was used to lower the bags through to the bottom into mud chamber. Approx 7 lowers each leg of the descent.

In the mud chamber the floor becomes very slippy and slidey. Good fun but very filthy!

At the sump Nat kitted up in the water. To silent onlookers and flashing paparazzi! Identity exposed as superman!

At 14:40 I descended into the Sump.

Following Martyn Farrs orange washing line. Last Layed in 13th August 1978.

The line drops into a large Aven, approx 8m wide with drainage scoring marks all along it. And descends rapidly to 13.0m

Here the bottom is met and a junction is encountered.

I have since reviewed my materials and it looks like this is line from 1985 by Joe Corrigan and Matthew Terry.

Cannot find reference to Arthur diving it. Might still be in my materials will double check.

I followed this newer line marking my exit side with a clothes peg. It stayed at 13.5m continuously until I reached a loose belay where the line had been washed back.

I attached my reel and set off to find the continuation.

I reached the end of the room at 13m and did a sweep of the chamber to check for side passages.

I regained my line after looping so reeled back to my last belay and then pushed on.

The roof was low and didnt look to continue further but I pushed myself feet first through a descent. The restriction began at -16m and opened at -18m

From here I was running out of line so I belayed a final tie off and cut the reel for home.

I had 20bar of usable gas to continue but didn't want to faff and knew I had a solid tie off.

On the return I decided to follow Martyns line onwards. Here I encounter a second line running parallel so with both running through my hands I swam on. At -14.5m the lines began diverging. Not wanting to select one and or risk entangling with the other I decided to make a retreat since I had 0m visibility in this section of the cave.

The passage is again very wide.

On return of both I surveyed as I went. This has since been compiled and my extension was made to the Upstream side of the cave. Towards Pollasillagh. Another critical missing connection of the marble arch system. Exciting to see that it is still wide open.

I performed a nice long safety stop and took the time to circumnavigate the aven since I knew I would have effort on the surface.

It took me about 1hour of work to carry my bottles back to the rift through the mud chambers. Many breaks taken, even some sensory deprivation sump floating with no lights and the sounds of running water.

Amazingly, just as I finally landed what I thought was the last bag at the rift I head movement and others of the group had returned to help me lift out the remaining bottles.

Someone had taken out the lift line when they originally left the cave.. it is on video!

Please leave the line in Situe in future 😊.

We made our exit ~17.30 when I last checked.

While I was diving the others had visited Pegleg and Freda's and got some ladder usage and tight spaces training 😁.