Since coral reefs are depleting, causing a great worry, 3D printed reef were implanted in the Persian Gulf, which sunk there in 2012. Scientists are now looking forward to 3D Print coral reefs made of porcelain coating to serve as real-like corals for ecosystem to be maintained.

Source: http://www.theatlantic.com/science/archive/2016/03/saving-coral-reefs/473844/