Scuba Diving the Highest Lake in South Wales

There is a Llyn (lake) in South Wales, UK that has a murky and dark history. The Llyn is located on the Northern Flanks of the UK’s highest Red Sandstone Mountain, and the highest mountain in the Brecon Beacons — the playground of the British SAS.

The Llyn is known as Llyn Cwm Llwch and is quite remote, the nearest road head is two miles away, and as described by the National Trust;

‘The wild, remote landscape of the central Brecon Beacons seems an unlikely place to suddenly find the calm, lapping waters of a lake. But if you look north-west from Corn Du or Pen y Fan, just where the steep, northern glaciated slopes start to fall away more gently, Llyn Cwm Llwch captures the eye.‘

Llyn Cwm Llwch is the best-preserved glacial lake in South Wales and sits right at the head of the Cwm Llwch valley — part of the Brecon Beacons Site of Special Scientific Interest (SSSI) and a Geological Conservation Review (GCR) site. I have passed this lake many times from the ridges of the surrounding mountains, so I decided that I was going to go and dive it. I’d no idea if it had been dived before, and I’d no idea of its depth or anything. All I knew is that it looks stunning from the surrounding mountain ridges and the weather is good just now so I’m going to make the most of it. Therefore, I arranged to do a Solo dive in winter.

I live an hour south of the Llyn. Logistically the expedition can be completed in a long day, so that’s what was planned.

I had already pre-packed the car and my 11yr old son Joshua was coming with me to help carry kit and take pictures, so it was literally a case of locking up the house, jumping in the car, and off we headed. The road is simple enough for the first two thirds of the journey, however the last third is through narrow single lane tracks, often squeezing past the trundling tractors, or as was the case today, past the heard of cows being ushered back to pasture post milking.

We arrived at the road head to a small National Trust car park and met our friend Adam Wedgbury, who had agreed to support my crazy adventure. This is at an altitude of 260mtr above sea level. The view from the car park onto the Northern flanks of the mountains was breath-taking, with the cloud shrouding the high mountain ridges. This morning the mountain stood proud in the morning light, casting its gloomy foreboding shadow towards us, almost as if it was daring us to really venture up into its flanks.

I had prepacked the kit into rucksacks that were manageable. As a mountaineer, as well as a diver, I had coined a phrase from the mountain world of going alpine style — which basically means extreme lightweight. I had packed just exactly what I needed for the trip and nothing more as two miles is a long walk, uphill, with packs on our backs. My pack weighed in at 22kg, plus I carried my 10kg weight belt. Adam carried 19kg and Joshua carried some kit, including wearing my dive helmet and the essential food and drink weighing in at a respectable 6kg.

We set off following the dirt track, which initially was fine and easy enough walking. As we plodded along the route, I told the guys of the factual story of a young lad called Tommy Jones. The story is that of a miner and his five-year-old son who were walking from Brecon town to the Grand parent’s farm, called Login, located in the valley of Llyn Cwm. They had stopped at a military training camp located nearby for a rest and drink, and by chance the grandfather and elder brother arrived. The elder brother was sent back to the farm house to let the grandmother know that guests were coming for tea, the younger brother followed him up the valley. The elder boy returned to the camp within a short time, but the younger brother never appeared. Everyone searched for the lad, including the army, but sadly he wasn’t found until twenty nines days later. He was found overlooking this Llyn, from the ridge nearby. An obelisk now marks the spot where he was found. Kind of puts a serious note onto the expedition and its location.

The track turned into a trail and then into a dirt path that meandered up the valley. Thankfully two miles wasn’t too far and within 45minutes we were at the Llyn.

We setup our base camp for the day, which consisted of somewhere to dump the bags and kit. I had thought about trekking up in my under suit, to save having to carry extra layers of clothing, however I had changed this plan as I didn’t want it to be sweaty and damp once I arrived. Being at 585mtrs above sea level the dive is considered an altitude dive, so both of my computers had to be setup to reflect that.

In the summer passing hillwalkers have been known to bathe in the Llyn, but I’m not sure if its been dived in Winter before. The Llyn is know for Leaches and Newts during the summer period, but I couldn’t see any today, sensible creatures!

I laid out all my kit to check it and assemble it. As it was a solo dive, I had brought just a seven-litre cylinder for back gas, and a three-litre cylinder for emergency gas in the form of a pony. There were a few hillwalkers on the mountain, who stopped to stare at us setting the kit up. I’m not sure if they were impressed or bewildered at the thought of us going diving in the lake.

The sky was clear at our level, but there was still a high level of cloud around the ridges, so it gave it a lovely atmospheric, almost mysterious feel to the adventure.

I got changed into my dry suit, Adam helped me into the harness and we ran through my safety checks. All was good. With that I walked into the lake, had a look around at the majestic situation I found myself in as the mountains towered above me, and descended.

First thoughts were — its freezing! The water registered as two degrees on my computer, and it certainly felt it as well. The bottom of the lake was a mixture of grasses and rocks. There was nothing exciting to see in the lake, not that I expected there to be, but it was definitely an interesting location. I didn’t see anything alive in there either, not that I expected leaches and newts to be swimming around enjoying the two degrees temperature.

The water was a murky brown colour, and the deeper I descended the more the colour changed from a brownie green to a brownie yellow. The brown colour came from the water ruining into the llyn from the surrounding Peat covered mountain side.

I didn’t spend long in the lake as my mission was to dive it not freeze in it! Once the dive was complete, I got out and after sorting out all out kit, we loaded it all onto our backs and headed back down to the cars — mission complete!

Again, I love diving — and the reason for diving strange and wild places is because they are there, it’s an inherent desire in all of us to explore and have adventures. For me, I guess I am an explorer/adventurer at heart and the thought of slogging up a mountain, diving an icy lake and slogging back down again really does excite me. Its not for everyone, and I would suggest that if divers are planning to go and do crazy adventure like this, they plan it well and check their knowledge of the type of diving they are going to do.

It’s not the diving that is difficult, the diving is just diving. It’s the theory behind what you’re planning to do. It’s an altitude dive, so how does that affect your dive planning? What about additional exposure protection? What happens if something goes wrong in these remote locations? Lots of things to consider.

However, once you have the planning sorted, and are happy that you are confident and suitably prepared for the challenge — go and enjoy yourselves as life’s too short not to!

Safe diving!