TEMPERATURES consistently above 30 degrees have prompted an increase in the number of people looking to cool off in one of the many waterholes on the Northern Rivers but police have warned swimmers to be wary.
Police said while the clear waters made for popular destinations, many people have died while swimming at the idyllic locations.
In January, a 19-year-old Illawarra man drowned while swimming at Hanging Rock Falls near Nimbin.
A 14-year-old boy died at the same waterhole in 2010.
In January 2014 a 31-year-old man died while swimming at Dalwood Falls near Alstonville.
Bexhill Quarry is another popular swimming hole but in 2002 tests revealed the pH level of the water was almost as acidic as vinegar and it contained aluminium levels 2500 times greater than the Australian guidelines.
Graham Lancaster from Southern Cross University tested the water again in 2014 and found that the pH levels had experienced a "marginal improvement" to 3.83. The aluminium levels had also decreased from 12.453mg per litre to 1.052mg per litre since 2002 but were still considerably higher than the Australian standard of 0.200mg per litre.
Earlier this month the popular Rileys Hill Quarry swimming hole near Broadwater was fenced off to the public after the Department of Primary Industries deemed it unsafe.
Lismore police inspector Nicole Bruce said people need to be conscious of the dangers associated with swimming in waterholes.
Insp Bruce said officers had attended a number of fatalities at several waterholes around the region in recent years.
"Waterholes are highly dangerous areas to be swimming in," she said.
"You don't know what's underneath the surface of the water and the conditions change constantly.
"Waterholes are often in an isolated area and if anyone gets into trouble help is often a great distance away."