Baptist University researchers on Thursday said they have discovered three previously-unidentified coral species in the eastern waters of Hong Kong, including one that could be exclusive to the SAR.

The three new sun coral species – which the researchers named Tubastraea dendroida, Tubastraea violacea and Tubastraea chloromura – are orange, purple and green in colour respectively, and resemble strings of firecrackers or clusters of tubes.

Qiu Jianwen, a biology professor at the university, said the coral species are small in size, with the largest one only measuring 20cm in height.

The expert said they were found in waters off Sung Kong and Waglan Island.

"They are not the most common species; we don't see them in every dive. Currently we have only seen them at these two locations," he said.

Qiu added that while two of the new coral species may be found in Japan and the western Pacific Ocean, the green one, Tubastraea chloromura, is currently only known to inhabit Hong Kong waters.

He said the new species, living at depths of between 10 and 30 metres, would use their colourful tentacles to capture zooplankton in the sea, unlike reef-building corals that produce nutrients through photosynthesis.

"They were in good health condition, as you can see from their very well extended tentacles in the field, and from the condition of their tissues."

He said his team came across the coral species during a study of coral-eating sea slugs, and members are optimistic that more such discoveries will be made in future.