Wildlife experts in south China are trying to rescue an endangered white dolphin that is in worsening health after mistakenly swimming into a freshwater river a week ago.

The Chinese white dolphin, about 30 years old, equivalent to 70 human years, swam into the BaishaRiver, a tributary of the Pearl River in Jiangmen, Guangdong province Feb 1. The animal is in a stretch about 100 km from the river's estuary. The species is under China's top protection list.

A rescue team comprising personnel from a local nature reserve and fishery authorities have attempted several times to drive the creature back to the sea without success.

"As it is too old and has been stranded for many days, the skin of the dolphin is festering and its health is deteriorating... its area of movement is shrinking," Feng Kangkang, a worker with Jiangmen Chinese White Dolphin Nature Reserve, said on Thursday.

Driving it back to sea should cause the animal minimum harm, but the dolphin has repeatedly swam back into the river due to weakening bodily functions, according to Feng.

The team is watching the dolphin round-the-clock and recording its health conditions, according to the Guangdong provincial ocean and fishery department.

White dolphins rely on echoes to identify the location of objects in water, but when they get old or suffer disease they are likely to run aground.

Each year, Guangdong reports two to three cases of senior white dolphins mistakenly entering freshwater rivers.

Chinese white dolphins are mainly exist only in small numbers, with about 2,000 detected at the mouth of the Pearl River.