It's the world's largest living organism but over the past 30 years Australia's Great Barrier Reef has lost nearly half its coral.
Now scientists have started harvesting and freezing coral sperm to stop the animal species from dying out.
They hope that in years to come they'll be able to re-introduce the coral spawn back into the damaged reef.
Dr Rebecca Spindler from Taronga Zoo in Sydney helped set up the sperm bank.
She says harvesting the coral's sperm is relatively easy.
Three days out of every year the Great Barrier Reef gives off all of its eggs and sperm - the only reproductive event that can be seen from space.
Researchers are hoping there is sufficient diversity within the coral they have harvested to not only re-introduce it to the reef, but also to select species resistant to extreme temperatures and acidity.
