Scuba divers in Indonesia were thrilled to see a school of giant manta rays drifting casually past them.
But even more amazing was the fact that one of them was entirely black, except for a few white spots on its underbelly.
These mantas typically have white underbellies and white markings on their backs.
Referred to as melanism, it is highly unusual in marine species.
In terrestrial animals, it is much more common.
AN example is black panthers, which are actually jaguars with a colour differentiation.
Although this phenomenon has been occurring more frequently in recent years, it is specific to manta rays.
No other shark or ray species exhibits this melanism.