Life saving equipment was damaged in an arson attack at Annalong marina in the early hours of Monday morning.
A life-ring in the area was set alight around 5.30am and completely destroyed, while another was damaged.
The fire was quickly extinguished by a man who lives nearby before police and the fire service arrived on the scene.
Chairman of Annalong Community Enhancement (ACE) and Newcastle Coastguard member James McKnight said a local man in his 20s had admitted to carrying out the attack and it was now in the hands of the police.
He said the man had been captured on CCTV which was also being provided to police.
Mr McKnight told the Belfast Telegraph that the man had offered to pay for the damage, but that it would otherwise have to be covered by Newry, Mourne and Down District Council.
"I was surprised someone of that age would be involved in this type of activity they really should know better," he said.
"A man who lives right beside the life ring noticed the fire and went out and extinguished it by himself. Bins in the area and another life ring were also targeted so they seemed to be going on a mini-rampage leaving a trail of destruction.
"We liaised with local DUP councillor Glyn Hanna who said the council would cover the expense, which is something we really don't need more of at this time. We hope to have it replaced in a matter of days."
Mr McKnight said the rings had saved lives in the past.
"We have been called out to incidents in the past where we have used the life rings and they have saved people, you can try and put a price on it but when it's needed and someone's life is at risk it's priceless" he said.
"We patrol that area regularly and this particular life ring is in a key location near the river.
"We would appeal to people to leave the equipment alone. We have been working to improve this area for a number of years and when something like this happens it feels like a real step back."
A Northern Ireland Fire and Rescue Service (NIFRS) confirmed one appliance was sent to the scene.
"Firefighters were called to a life ring on fire on Harbour Drive. Firefighters used one hose reel jet to extinguish the fire," the spokesperson said.
"The cause of the fire was deliberate ignition and the incident was dealt with by 6:20am."
A PSNI spokesperson appealed for anyone with information about the incident to come forward.
"Causing damage to such an important piece of equipment is unacceptable and shows a total disregard for the safety of the community in Annalong. Life rings could be the difference between life and death for a person, who may be in difficulty in the water" the spokesperson said
"Police are keen to speak to anyone who may have witnessed this incident, including two persons in the area at the time of the incident who may be able to assist police with their enquiries to contact police on 101 quoting reference 223 of 16/03/20.
"Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime."