Seagrass in the world’s oceans is a vital part of the ecosystem: it captures carbon faster than rainforests, protects coastlines from erosion, and provides habitat for countless species. In the United Kingdom, however, up to 90% of these underwater meadows have already disappeared. Project Seagrass aims to restore seagrass populations. Initially, divers manually cut and collected seed pods one by one. As this process was labor-intensive, costly, and difficult to scale, the idea emerged to develop a tool that could make harvesting safer and faster.
To achieve this, Project Seagrass partnered with Tandem Ventures, a company specializing in developing purpose-driven inventions funded through brand partnerships.
In this case, the goal was to design and build an underwater harvesting machine: a sled towed behind a boat that cuts the tips of the seagrass where the seed pods grow and brings them to the surface.
The device needed to operate gently enough to avoid damaging the seabed or marine life, yet robust enough to function in harsh ocean conditions. In addition, the team had only a few months before the seagrass season ended. The first prototype consisted of a trash pump, two sealed plastic barrels, and several flexible hoses. Regular soaked “land grass” cuttings were used to simulate seagrass. The result: a “grass smoothie” and a blocked pump. The barrels collapsed under suction.
Next, the cutting blades were tested. With permission from a local farmer, the team used a hydraulically powered trimmer blade from the trunk of a car, and later on by foot, to determine the optimal cutting speed of about one knot. The tests also revealed that the separation system would require more intellgent filtration, reinforced barrels, and a safety guard for the blades.
Highly Efficient Team Collaboration
The entire harvesting machine was developed collaboratively in Onshape, a cloud-native CAD and PDM (Product Data Management) platform. This enabled all team members to work together in real time from anywhere, on laptops while traveling, in the workshop, or on boats. Real-time version control, commenting features, and simultaneous editing allowed Tandem Ventures’ design team to iterate quickly and securely. This proved crucial in a fast-paced, experimental setup where the design evolved daily between testing phases.
At the heart of the harvesting machine is a compact underwater data logger featuring an orientation sensor (EVAL-ADXL366Z) from Analog Devices, an ESP32 microcontroller, and numerous additional components from Mouser Electronics. The system records depth, orientation, pressure, turbidity, and temperature, providing researchers with critical feedback.
For custom components such as hinges, leg joints, cable guides, fins, and protective covers, the team collaborated with Bambu Lab. Its H2D printer is capable of producing large, industrial-grade components from durable TPU and PLA materials. The entire sled structure was assembled using a wide range of marinegrade stainless steel fasteners from Accu Components, specifically selected to withstand harsh saltwater conditions.
Field Test in a Welsh Bay
The prototype was deployed from a boat into Porthdinllaen Bay in North Wales, one of the UK’s most valuable remaining seagrass meadows. An experienced member of the seagrass team assessed the test environment to ensure safe and suitable operating conditions. Testing was limited to a few short harvesting runs to validate the concept while minimizing environmental impact. A small number of seed pods were successfully collected using the team’s new harvest pump filtration system.
Based on the test results, further improvements were made: robust, extendable legs for precise cutting-height adjustment and emergency zip-access panels to allow divers safe access away from the blade to remove accumulated grass, debris, or blockages. A blade guard, 3D-printed in flexible and durable TPU using Bambu Lab technology, ensures that only seagrass comes into contact with the sharp blade while keeping larger objects away. Tandem Ventures is also developing a completely new pump system to increase reliability and simplify operation.
The harvesting machine prototypes have the potential to enable Project Seagrass to collect seeds up to 100 times faster. Onshape will continue working with Tandem Ventures and Project Seagrass to further refine the prototype and develop a faster, more efficient solution to help preserve and restore seagrass meadows.
Hannover Messe 2026 Exhibitor: Hall 17, F36
