Post uncovered: Milk VFX on Under Salt Marsh

Milk VFX delivered 662 visual effects shots for Under Salt Marsh, supporting the project from early concept development through to final compositing.

Guided by director Claire Oakley’s vision, the brief called for expansive environments, dramatic weather and significant digital world-building.

Working closely with Milk Production VFX supervisor Mark Harris, production VFX producer Patrizia Mule and Milk VFX producer Jasmine Ford-Elgood, the team delivered large-scale environment builds, complex weather simulations and compositing in support of Oakley’s vision of a place that felt entirely authentic and grounded.

The work began with concept designs for drone shots showing the town of Morfa Halen before and after the flooding. These were developed into digital matte paintings using a lidar scan of the real town as a base, before moving into compositing where the environments were carefully integrated into the drone-shot plates.

More than 100 shots required digital extensions to the practical town set. Milk created concepts to define how the set should expand beyond what was physically built, which were then developed by the environments team using lidar scans of the studio backlot, bespoke house and street models, and photo-scanned assets captured on location in Wales by Milk’s VFX Supervisor and on-set team.

A key part of the story was the construction of a seawall. While part of this was built practically on set, it also required significant digital extension, with the environment team expanding the structure and surrounding landscape and the compositing team seamlessly integrating the CG work into the plate photography.

Milk’s biggest challenge was the weather work. As the story evolved, the scale of the storm continued to grow throughout the edit and into post-production. The ocean work was particularly demanding due to the use of wide-angle drone photography, which required vast expanses of simulated water. Milk’s FX team simulated miles of turbulent ocean in Houdini, with storm-driven waves crashing against the shoreline and sea defences.

Dozens of simulations, including foam, bubbles, splashes and water interaction, were layered together in compositing to create a cohesive and photorealistic result, with the most complex shots combining low-flying camera moves close to the ocean surface while still revealing huge distances into the horizon.

“The storm work was the most complex aspect of the show,” says production VFX supervisor Mark Harris. “Simulating miles of ocean and integrating that work into wide-angle drone photography, often shot in calm conditions, was a huge challenge, and one the team rose to.”

The storm reaches its peak in Episode 5, as rising water threatens to breach the seawall. Much of this sequence had been shot in fine, sunny conditions, requiring extensive sky replacements, added rain, atmospherics and rough water to sell the intensity of the storm. Stormy seas and skies were added throughout Episodes 5 and 6, alongside large amounts of rain work and, in some cases, snow.

Several establishing shots were created to define the geography and character of Morfa Halen. One extends the view of Spider Island, revealing houseboats sitting among the marshlands backed by the Welsh mountains, achieved using a mix of projected DMP backgrounds and 3D environment builds. Another wide establisher features Kelly, Rafe and Brian in a small patch of practically built marshland, shot as a locked-off plate, with Milk’s environment team digitally extending the marsh and compositing adding a camera move to reveal a dawn horizon created as a digital matte painting.

To support delivery across the series, Milk collaborated with sister studio Phantom FX, part of the Phantom Media Group, who delivered 200 VFX shots across seven sequences. Working closely with the Milk team over six months, Phantom FX handled compositing, set integration and CG rain work, contributing to the smooth delivery of all six episodes of the acclaimed series.