Project Seagrass: These Screws Restore Ocean Meadows
What happens when a small creative engineering studio, solving global problems through design, takes on a marine conservation challenge? Innovation that gives rise to one of the most promising tools for ocean recovery yet.
Led by Project Seagrass, with support from Tandem Ventures and partners including Accu - the development of a small, bright-yellow underwater machine may hold the key to restoring the UK’s vanishing ocean meadows.
These meadows - vast networks of seagrass that thrive beneath sheltered coastal waters - are the lungs of the ocean. They capture carbon up to thirty times faster than rainforests, stabilise sediments, and provide sanctuary for juvenile fish.
Yet today, up to 90% of the UK’s seagrass has been lost. Restoring it is a race against time.
That race has inspired a breakthrough in subsea engineering: the world’s first underwater seagrass harvester.
Engineering Hope: The Birth of the Harvester
Until now, collecting seagrass seeds was painstakingly manual. Divers spent hours underwater, hand-cutting and bagging seedpods - a slow, costly, and physically demanding process.
To scale restoration, the team needed a safer, faster method that could harvest seeds gently without damaging the delicate seafloor.
Enter Tandem Ventures, specialists in practical inventions for social good. Partnering with Project Seagrass, the brief was ambitious but clear: design and build a towable underwater sled capable of trimming the tips of seagrass blades, collecting seedpods, and filtering them to the surface - all within months, before winter storms washed the meadows away.
The challenge wasn’t just technical. It demanded a solution robust enough for the harsh marine environment, yet delicate enough to preserve life beneath the surface.
From Sketch to Seafloor: Iteration in Action
Early prototypes told a familiar story of trial, error, and discovery. 
The first concept used makeshift components - a pump, flexible pipes and plastic barrels - to test whether seedpods could be drawn safely through a filtering system.
The result? A vivid green “grass smoothie” and two imploded barrels. Valuable lessons followed: stronger filters, reinforced housings and a safer approach to cutting.
As the concept evolved, precision became everything. Designed in Onshape, a cloud-based CAD software used in professional product design, the digital 3D model captured every detail - from adjustable legs to protective blade guards.
For high-strength, lightweight components, the team turned to Bambu Lab’s H2D 3D printer, producing large-scale parts in durable TPU and PLA.
Holding the entire machine together was a network of marine-grade stainless steel fasteners from Accu - essential for resisting corrosion, ensuring safety, and keeping every joint stable through high-pressure underwater operation.
From M6 Torx screws on the frame to 3mm Polyfix screws securing the onboard data-logger, these components maintained their integrity and shine even after prolonged immersion.
Precision Components at Depth
Every element of the harvester’s construction demanded reliability. Saltwater corrosion, vibration, and shifting pressure can all compromise connections - making fastener quality a defining factor in the project’s success.
Accu’s marine-grade stainless steel fasteners were selected for their exceptional resistance to saltwater oxidation and their proven strength in mechanical assemblies exposed to extreme conditions.
Their precision engineering ensured secure fittings across moving and static parts, while also simplifying disassembly for cleaning and maintenance - crucial for field trials in remote coastal locations.
The result was a system that performed exactly as designed: watertight, resilient and maintainable by divers and engineers alike.
Trial by Water: Porthdinllaen Bay
The first real-world test took place at dawn in Porthdinllaen Bay, North Wales - one of Britain’s last surviving seagrass meadows. With licences secured and conditions calm, the bright-yellow prototype, nicknamed Thunderbird 4, was lowered gently into the sea.
As the pump started and the cutter hummed, fragments of seagrass began flowing through transparent tubing. Within minutes, seedpods collected in the twin-barrel filter system - proof that the concept worked. The trials were intentionally brief, designed to capture data and refine performance while leaving minimal environmental footprint.
From that small collection of seedpods, a scalable future began to take shape.
Refinement Through Innovation
Subsequent iterations introduced refinements based on field data. Reinforced extendable legs allowed for precise cutting height adjustment. Quick-access zip hatches enabled divers to clear blockages safely. A 3D-printed TPU blade guard shielded wildlife while maintaining efficient cutting performance.
These continuous improvements point toward an extraordinary outcome: a harvesting process that could be up to 100 times faster than manual collection - transforming the scale of global seagrass restoration efforts.
Collaboration for a Living Ocean
The success of the harvester is the result of collaboration between organisations united by purpose.
Project Seagrass, a leading UK conservation charity, provided ecological expertise and restoration guidance.
Tandem Ventures drove the design, testing and coordination. Industry partners - including Accu, Aviva, Bambu Lab, MiWorld Services, Mouser Electronics, Analog Devices, Onshape and Tappable - contributed their products, technology and time.
Together, they demonstrated how engineering innovation, when paired with environmental commitment, can deliver meaningful conservation at scale.
“Thank you from us, and the entire Project Seagrass team, for Accu’s support in making this project possible.”
Edwin Towler & Sam Rogers
Tandem Ventures
Engineering for a Better Future
At its core, this project exemplifies the power of precision engineering to support the planet. Accu’s components, built for durability and accuracy, are helping engineers and scientists develop real-world solutions to environmental challenges - from the skies above humpback whales to the seabeds where new meadows are taking root.
By enabling progress one fastener at a time, we’re proud to support projects that restore balance beneath the waves - and safeguard the future of our shared oceans.
Further reading.
- Arribada Conservation - Creating Open & Accessible Conservation Technologies
- Mission Humpback - Learn how Accu helped Tandem Ventures & Whale Wise to develop a LiDAR-enabled drone to monitor Humpback whales in Iceland.
FAQs
Q: What makes seagrass restoration so important?
A: Seagrass meadows absorb carbon, stabilise coastal sediments, and provide vital nurseries for marine species. Restoring them is critical to reversing biodiversity loss and mitigating climate change.
Q: Why were marine-grade stainless steel fasteners used?
A: They resist corrosion from saltwater, ensuring long-term durability and safety for subsea machinery operating in extreme environments.
Q: How does the harvester improve restoration efficiency?
A: The system enables up to 100× faster seed collection than manual diving methods, making large-scale restoration feasible.
Q: How can I support Project Seagrass?
A: Visit Project Seagrass to learn more or contribute to their ongoing conservation efforts.