Divers are assembling biodegradable materials with several coral colonies in the tropical coral reef of Burgers' Ocean aquarium in Arnhem, the Netherlands.

The modular blocks can be interlocked to create underwater artificial reef structures of different sizes and complexity.

They were created by start-up Reefy, which is based in the western city of Delft, to create flourishing coral reefs and restore the marine ecosystem while protecting shorelines from waves.

Having conducted tests at the aquarium's coral reef, which imitates a natural Indonesian reef, Reefy will soon use its techniques to restore reefs in the wild.