Coral reefs.

Corals are simple and archaic animals called polyps. Their small body has a ring of tentacles that have stinging cells which help them catch small animals for food. Corals also have the ability to make skeletons for themselves out of limestone which in turn helps with support as well as the maintenance of reefs. The polyps usually grow upward, resulting in the expansion of their skeleton and as they grow they also divide by developing "…

…the National Action Plan for Coral Reef Conservation, which summarizes strategies that can be used to deal with issues that threaten coral reefs. The group also meets often to talk about their progress and new ideas that can be used to help. Other associations also try and help restore coral reefs. Some of their "efforts include creating isolated marine sanctuaries, transplantation of reefs, forms of electrolysis to advance growth and restrictions on harmful fishing techniques."