The Big Brenig Swim

Sitting at an elevation of 370 metres above sea level, Llyn Brenig acts as a vast, open bowl that funnels the winds sweeping across the Denbigh Moors. For the swimmer, this means a surface that often turns into choppy water, demanding a steady stroke and a clear head. The reservoir is an artificial expanse created by damming the valley, a project engineered by George Deacon, whose previous work on the nearby Alwen Reservoir set the precedent for water management in this high-moorland region. Because the area is prone to sudden weather shifts, the course—marked by a linear series of inflatable buoys—can feel exposed, making a tow float a prudent choice even for those comfortable in rougher conditions.

The landscape from the water

As you navigate the 2.5km or 5km routes, your perspective is framed by the rugged contours of the Mynydd Hiraethog uplands. On the horizon, the summit of Mwdwl-eithin rises to 532 metres, a point marked by a stone shelter built to protect hikers from the very storms that stir the lake’s surface. Looking toward the shoreline, the scenery shifts between open moorland and the dense greenery of the Clocaenog Forest. This woodland is one of the final strongholds for red squirrels in Wales, and while you are focused on your navigation, the forest edge remains a constant, dark backdrop to the eastern side of the reservoir. Between the water and the surrounding peaks, the Hafod Elwy Moor reserve serves as a sanctuary for ground-nesting birds; if you pause at the feed stations or during sighting, you might catch the silhouette of a peregrine falcon or a hen harrier circling the higher slopes above the water.

Historical passage and race logistics

This landscape has long served as a transit point for those crossing the Welsh interior. Near the village of Cerrigydrudion, the historic farmhouse of Ceirnioge Mawr once acted as a vital staging post for mail coaches along the A5 route to Ireland. A plaque at the site commemorates a visit from Queen Victoria, who stopped here while travelling through the region. Today, the Big Brenig Swim brings a modern intensity to these moors with a limited field of 300 entrants. The event, held in mid-September, requires a cautious approach to water safety, dictated by the reservoir's depth and exposure. Whether you are tackling the 500m sprint or the full 5km endurance challenge, the experience is defined by the requirement for self-sufficiency and respect for the unpredictable moods of the mountain water.