The town of Morfa Halen takes centre stage to multiple tragedies as Under Salt Marsh begins. With the mysterious death of a nine-year-old boy weighing heavy on the area, just three years after the disappearance of a nine-year-old girl, this tight knit community is soon falling apart at the seams.

To add to the tension, Morfa Halen – based on the edge of Wales – is running dangerously close to disappearing completely, with a sea wall being the only defence from the town going completely underwater should a heavy-enough storm hit the coast.

While the village might be fictional, the reality is far too real, and it was up to Stevie Herbert to bring every element of Morfa to life, cementing the importance of the community and the area to the story as it plays out.

Speaking ahead of the series, Herbert opens up about her thoughts on the script, how the landscape her shaping of Morfa Halen, and the unique touches she made in the creation of the set to make it perfect.

I remember thinking it was a very unique world. The scripts felt incredibly current, dealing with themes like climate change and the fragility of coastal communities. It was like images we see in the news — towns under threat, people fighting to preserve their homes.

But it also had this evocative sense of island life, something quite poetic and atmospheric, which made it a compelling canvas to build from.

From a designer’s point of view, it was a dream. The world is so multifaceted — landscapes, community spaces, homes, and even an amusement park. It’s rare to find a drama that encompasses so many strands.

Within 48 hours in the story, so much happens to this community, and that gave me a rich, dynamic environment to build. It’s a world on the edge of the world, and that sense of isolation and urgency was very exciting to explore visually.

It’s incredibly diverse and deeply influenced by the landscape. We started by inventing the island and the causeway — heading north in Wales, where the land gets cut off regularly. That created a sense of ethereal isolation. Our early conversations were all about how people live alongside the land, how their lives are shaped by it. The salt marshes, the village centre, the mountains — they all informed the visual tone.

It’s a world that feels real but also slightly heightened, with a strong sense of place.

Yes, absolutely. One of our earliest guiding ideas was to design the world with its destruction in mind. Morfa Halen floods during the story, so we had to build knowing that everything would eventually be dismantled or submerged. That meant thinking about how the environment — water, wind, marshes — would impact every space. It shaped everything from material choices to structural integrity. The elements were always part of the design conversation.

The centre of town was the most impacted. We couldn’t flood a real town, so we built one. That gave us creative control — we could shape it visually to reflect the characters and the emotional stakes. But it also had to be physically functional. We built it in a tank so it could flood gradually.

First, it’s a dry shoot with people going about their day — visiting the butcher, walking through the chip shop — and then it transforms into a dramatic flood zone. It was a huge technical and creative challenge.

It was sobering. We filmed in areas like Barmouth and Fairbourne, which are genuinely at risk. But Morfa Halen is a creation — it doesn’t exist. We cherry-picked elements from real places and built a town that felt authentic but also served the story.

The salt marshes, the skies, the mountains — they gave us the natural drama we needed. Morfa Halen became a small, special pocket of the world, a place that feels timeless and deeply rooted, which makes its vulnerability all the more poignant.

We started with the natural palette of North Wales in winter – think misty greys, soft blues, earthy tones. But we wanted to bring vibrancy too. Adam, our cinematographer, talked about “pops of colour” — reds, yellows, greens, blues — that would stand out without overwhelming the frame.

It’s a seaside town, slightly faded, with retro touches. We looked at references from the 50s and 60s, especially for the amusement park, which is brighter and more playful. Everything had to feel real, but with a touch of quirk.

The national park backdrop was stunning, it was such a rich landscape to work with. We also had fun transforming unexpected spaces, like turning a golf club into an ice cream parlour.

The central village build was a highlight. It had heritage and a slightly odd charm — some buildings looked like they belonged in a Mississippi swamp, which wasn’t intentional but added character. We even drew on Americana for reference. It was about creating a world that felt lived-in and layered.

We wanted people to feel emotionally connected to the town. That meant building spaces that felt real, like shops, post offices, places where people gather. One of my favourite elements was the butcher’s shop, which felt like it had been there for 150 years. We added details like Welsh slate, sash windows, and functioning interiors.

Claire is brilliant at spotting those small touches that make a place feel alive. We wanted viewers to understand why this community would fight to protect it.

Claire, as both writer and director, had a very strong sense of the story. We started with visuals — boards full of island life, waves, wind, and colour. She had a clear vision, and we quickly got on the same wavelength.

Adam joined early and brought a great instinct for the world we were building. It was a constant dialogue throughout the shoot, and a genuinely collaborative process. They both made it a fun and creatively rich experience.

Logistically, it was tough. No workshops, no prop stores, no quick fixes. We built out of car parks and had to plan everything meticulously. The salt marshes were especially challenging — tidal, dangerous, and environmentally sensitive.

We had to be careful not to disturb nature while dressing and building. The weather was unpredictable — howling gales, sideways rain — but it added to the authenticity. You needed wet weather gear and a lot of resilience.

I knew what a salt marsh was, but I didn’t fully grasp its environmental importance. It’s like a tidal sponge— absorbing water, preventing erosion, and protecting shorelines. When you’re in one, it almost turns into a waterway. Seeing it firsthand was eye-opening. It’s a vital ecosystem, and designing around it made me appreciate its role even more.

We were very conscious of sustainability. We reused materials, recycled set pieces, and returned props to local authorities. For example, the seawall and builder’s yard were repurposed by a local farmer for real sea defences. We dressed a school using local furniture and returned everything afterward. Even the rubbish we used for a quarry scene was bought from another production and will be passed on again. We tried to make every element count.