Yobs threw the life ring at Pimley Manor fishing pools in Shrewsbury into the River Severn and burned its casing.
Shrewsbury Anglers Club looks after the waters along that stretch of the river, and secretary Chris Wood said that such behaviour is risking lives.
He said: "We discovered that some moron had set fire to the life ring holder and the life ring was missing.
"This is not even a public footpath, despite local people thinking they have the right to walk over it including walking straight through newly planted crops.
"Last year signs were put up advising no access and private property and all pulled down within 24 hours.
"The land owners have had enough and are planning on securely fencing and gating all possible access points with the exception of those permitted to the angling club which will have locks."
He added: "It's not the first time something like this has happened. Life rings have gone missing in other areas of the town. You hear about river deaths in Shrewsbury. When somebody needs a life ring, it's not going to be there.
"I don't know why people can't just enjoy the environment. It's always the minority that spoils it for everyone else. It's the same old story."
The club has also been left frustrated with littering along riverbanks of various fishing spots. In a recent litter pick, volunteers collected 13 bags of rubbish, only to find rubbish strewn all over the place again in a matter of days.
Chris added: "The mentality of some people leaves a lot to the imagination. Why?"
It comes after more litter problems have plagued the town, most recently in the Quarry over the Easter Bank Holiday weekend, when 25,000 litres of rubbish were collected by beleaguered Shrewsbury Town Council workers. There have also been a number of anti-social behaviour issues reported in the town, including several break-ins and violent incidents in recent weeks.