Coastal Curiosities: Strange and Wonderful Secrets of the Shore
Published on 28 Jul 2025 by Amy GreenwoodHave you ever wandered along the shoreline and found yourself captivated by something a little… odd? Maybe the sand squeaked beneath your feet. Or perhaps you spotted a magical glow in the waves after dark. From towering arches carved by wind and wave, to rocks that whistle, sands that sing, and seas that sparkle, Wales’ coastline is full of natural wonders.
But what causes these enchanting seaside spectacles? Behind every natural wonder is a blend of science, time, and the power of the elements. In this blog, we’re diving into the world of coastal curiosities – those fascinating features shaped by nature. From bioluminescence to bizarre rock formations, come and explore the quirks of Wales’ coastline – and discover the science behind the magic.
Bioluminescence: Nature’s Light Show
On summer nights, if the conditions are just right, you might witness a shimmering glow in the water, a curious light that shifts from vivid green to electric blue as the waves roll in. This magical-looking glow is caused by bioluminescent plankton, tiny organisms that emit light when disturbed. It’s one of the most extraordinary coastal sights you can see – if you’re lucky enough.
On Anglesey, sightings have been reported along quiet stretches of shoreline like Penmon Point and Lligwy Beach, where the absence of light pollution enhances the effect. Further south, the Llyn Peninsula and Ceredigion coast have seen the blue glimmers appear during warm, still summer nights.
So, what’s the science behind it? These plankton produce light through a chemical reaction involving luciferin – the same substance found in fireflies. It’s thought to be a defence mechanism, to startle and ward off predators. To us, it just looks like pure magic.
Tip: For your best chance to spot bioluminescence in Wales, head to a south-west facing bay on a warm summer night. Late at night gives you the best chance, ideally midnight to around 3am. Turn off torches and be patient!
Curiously Squeaky Sands
Yes, it’s true – some beaches really do squeak when you walk on them! Head to Porthor on the Llŷn Peninsula, affectionately known as Whistling Sands, and you’ll hear the famous squeak, or whistle, of the sand under your feet.
This phenomenon only happens when the beach is dry, and the grains of sand are just the right size and shape, almost perfectly spherical. When compressed by your footsteps, they rub together to produce the curious squeak.
There are only a handful of beaches in the world where this phenomenon occurs, and North Wales is lucky enough to have one.
Bonus curiosity: On very dry days, you might even hear a faint whistling as the wind moves across the dunes – giving the beach its whimsical nickname.
Sea Arches, Caves & Coastal Legends
Wales’ coast has been shaped by crashing waves, shifting tides, and the patient persistence of erosion which has created spectacular landmarks well worth seeking out.
On Holy Island, Anglesey, you’ll find a rugged stretch of coast where the sea caves, stacks and arches of Rhoscolyn tell a story of relentless erosion and ancient upheaval. Arches like the impressive Bwa Du (Black Arch) and Bwa Gwyn (White Arch) have been sculpted by the relentless power of the waves, exploiting natural weaknesses in the cliffs to form caves, then tunnels, and eventually full-blown arches. It’s geology in action – and the result is utterly breathtaking.
Further down the coast, rock stacks and caves continue the theme. Between Llangrannog and Cilborth, the striking sea stack ‘Carreg Bica’ (the Giant’s Tooth) stands just offshore. Legend says it is the tooth of the giant Bica who spat it out following a terrible toothache – but science says it is a harder chunk of rock left standing as softer material around it eroded.
These formations are a dream for photographers, but they’re also a lesson in the power of the sea and the ever shifting nature of the coastline.
Fun fact: The rocks around Rhoscolyn are part of the ancient Precambrian bedrock – some of the oldest on Earth, dating back over 600 million years!
Colliding Currents in Bardsey Sound
At the very tip of the Llŷn Peninsula, you’ll find the Bardsey Sound – a place of swirling tides, curious sea lines, and powerful natural forces.
If you head across the water to the Ynys Enlii (Bardsey Island), you’ll notice a clear line in the water – where two sea currents meet but don’t immediately mix. One side might be deep blue, the other a murky green. The contrast is so distinct it looks as though someone has drawn a line straight across the sea.
This curious visual effect is caused by differing tidal flows meeting at slightly different speeds or directions. Bardsey Sound is one of the best places to spot it, thanks to the strong tides that rush between the Llŷn Peninsula and Ynys Enlli.
Did you know? These converging currents create rich feeding grounds for seabirds, seals, and dolphins – making it a top spot for wildlife watching. It’s also the reason this particular stretch of water is notoriously tricky to navigate.
Shifting Sands and Submerged Forests
Lastly, head to Borth Beach, just north of Aberystwyth. Here, you might catch sight of an ancient forest, preserved in the peaty sands for over 4,000 years. Shifting sands, storms and low tides have previously revealed the haunting remains of a Bronze Age forest, said to be part of the mythical kingdom of Cantre’r Gwaelod, which was swallowed by the sea.
Tree stumps, still rooted, rise from the sand – a glimpse into a time when the sea level was much lower and this area was dense woodland. It’s a reminder that coastlines aren’t fixed. They move, shift, and sometimes reveal the past in strange and unexpected ways.
Top tip: For the best chance to glimpse Borth’s lost forest, visit at low tide – ideally in winter, when storms have been known to strip back the sands and reveal the hidden past.
Our coastline isn’t just a stunning backdrop – it’s a shifting landscape filled with natural wonders shaped by time, tide and the elements. From sands that squeak to seas that glow, from ancient forests to colliding currents, Wales’ shorelines are full of secrets just waiting to be uncovered.
So next time you take a seaside stroll, keep your eyes – and ears – open. You never know what strange and wonderful coastal curiosity you might discover.
