Many dolphins were spotted jumping out of the water and frolicking around a pilot vessel as three sailors returned from their work on Friday in Fangchenggang city in the Guangxi Zhuang autonomous region.

"There were, I suppose, dozens if not a hundred of them. I've never seen so many dolphins before and I felt so excited and recorded this rare scene with my phone." said Shi Decheng, one of the sailors.

"We were sailing pretty fast on our course back when we found the dolphins following us. But once we slowed down they fled to the southwest."

Chen Mo, assistant researcher from Beibu Gulf Marine Research Center of the Guangxi Academy of Science said, "We can tell that they are long-beaked common dolphins. They can be observed in Beibu Gulf every November, but we are still not sure why so many are here now."

The long-beaked common dolphin is a key protected animal in China, with an adult body length of 2 to 2.5 meters and an average weight of 80-150 kilograms. They feed on schools of pelagic fish typically within 200 meters of the surface and like to ride the waves near the bow of ships.

Most dolphins live in warm tropical waters and are picky about water quality.

In recent years, Bryde's whales, green turtles and dolphins have been spotted around Fangchenggang, indicating that its marine ecological environment is improving.

Xie Zhendong contributed to this story.