The Rotterdam Reef

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In collaboration with the City of Rotterdam, Rijkswaterstaat, and Boskalis, the innovative start-up Reefy from Delft will test a modular artificial reef system. This system protects the riverbank against large ship waves and stimulates the development of nature.

The Rotterdam Reef
From left to right: Sander Steenbrink (Boskalis), Petra de Groene (city of Rotterdam), Jaime Ascencio (Reefy) and Leon Haines (Reefy).


Reefy is a young company from Delft, the Netherlands, that combines biology and hydraulic engineering to develop nature-inclusive solutions for water safety.

Reefy’s innovation consists of massive “Lego-like” blocks, which have been hydrodynamically designed and tested in the Deltares wave flume. By assembling these blocks underwater, a stable structure is formed that breaks waves.

These blocks also create an underwater labyrinth where fish and other species can shelter and breed. The blocks are made of sustainable concrete with a special texture on the surface. With this, the start-up aims to stimulate all kinds of biological growth, such as oysters and mussels to create a living layer that promotes biodiversity.

And can grow with sea level rise, requiring less maintenance. Innovative materials to stimulate this are now being further tested behind the scenes in collaboration with Diergaarde Blijdorp.

The history of Reefy

The Delft start-up Reefy was founded by Jaime Ascencio and Leon Haines. Ascencio worked as an engineer in Mexico and the Caribbean Sea, where he sought sustainable solutions for resorts against coastal erosion. The current artificial reefs on the market turned out to be unstable and cannot be used as breakwaters.

To find a solution, he left for TU Delft to follow the Master’s in Coastal Engineering. Haines is a marine biologist who, after studying Integrated Coastal Management / Marine Biology, spent five years working on coral reef restoration projects on islands in Thailand, the Maldives, and Indonesia.

The Groene Poort (Green Gate): City of Rotterdam and Rijkswaterstaat

Since the end of 2013, the City of Rotterdam, Rijkswaterstaat, the Port of Rotterdam, and the World Wildlife Fund have been working together on sustainable, nature-friendly riverbanks in the Nieuwe Waterweg and the Scheur.

They do this, among other things, with clean residual material from construction. The project is called ‘De Groene Poort’ or ‘Green Gate’. To keep these natural banks in place and to protect them against the waves of ships and current, breakwaters are needed to create a foreshore. Rijkswaterstaat and the City of Rotterdam are looking for more sustainable solutions for this than the usual rock or stone dams. By testing these reef innovations in collaboration with Reefy, the City of Rotterdam and Rijkswaterstaat hope to find a resilient and sustainable solution to restore the natural values ​​in the tidal area of ​​the Maas river.


As an international leader in dredging, offshore wind, and maritime services, Boskalis is always looking for sustainable alternatives. Boskalis’ Artificial Reefs Program supports innovative start-ups in developing products to achieve large-scale positive impact. For the test set-up, Boskalis will help install the project in the Nieuwe Waterweg with large equipment and expertise. This project is also Boskalis’ fourth artificial reef knowledge development project under the Artificial Reefs Program.


In 2021, the Municipality of Rotterdam and Boskalis gave Reefy so-called ‘golden tickets’ to participate in the maritime accelerator program PortXL. In this program, startups and scale-ups are connected to potential customers and networks to test and market innovations. The Rotterdam Reef project, which aims at the chain from the production of blocks to monitoring of the reef, has arisen from initiatives from all parties to stimulate innovation.

Rotterdam Zoo Blijdorp

Blijdorp Zoo helps innovative companies by creating space as a testing ground. In collaboration with the Delft University of Technology, Blijdorp offers facilities and guidance for start-ups to develop new technologies. Reefy has worked closely with Oceanium in Blijdorp to develop its technology. Behind the scenes, the startup grows coral on various sustainable concrete alternatives to develop the perfect material for reef restoration. At the visitors’ side in the Science Aquarium, Reefy has placed a scale model of the reef that will also be installed in the Green Gate to educate visitors about the use of artificial reefs for wildlife restoration and the importance of reefs for coastal protection.

Cooperation agreement

The 4 parties signed a cooperation agreement on the 24th of June. The plan is to place the reef, the Rotterdam Reef, in October 2022. The technical stability and ecological development are then monitored to see the effects on nature and the functioning of the reef as a wave barrier.

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