An Australian company has 3d printed a reef and placed it in the Maldives.
It's printed in ceramic.
https://youtu.be/a6aFsPbtth0
World's largest 3-D printed reef installed at Summer Island Maldives | 3D... (https://www.3dprintingprogress.com/articles/15232/worlds-largest-3-d-printed-reef-installed-at-summer-island-maldives)