Two people have been rescued from the River Uck in the space of five days.
The most recent incident occurred in Uckfield on Thursday (December 6).
Firefighters were alerted to a man in the water shortly after 9.30pm. They carried out a river search and the casualty was located on the bank and given first aid.
The previous Sunday morning a woman was rescued from the Uck after going into the water to recover her dogs near Uckfield Rugby Club.
Water safety equipment was used to reach the victim and her pets, and she was left in the care of the ambulance service.
East Sussex Fire and Rescue Service has issued a reminder about the dangers of walking near a river or other body of water, particularly after dark.
A spokesperson said: “Water temperatures are dropping rapidly now and hypothermia is a very real danger to anyone not wearing the appropriate clothing.
“Another real issue is the unseen dangers that lie beneath the water’s surface that are not readily visible. With the murky consistency of the Uck you cannot see objects in the water and it is difficult to work out how fast the water is flowing.
“We strongly advise to avoid entering the water to rescue your pets and that if you come across a person in danger, in or near a body of water, dial 999 immediately with as much information as to the exact location as possible and please remember the ‘Shout, Reach, Throw’ principle to assist the person in trouble but keep yourself safe.”