A group of teens swimming at the reservoir and diving into the water got more than they bargained for yesterday - a visit from the police.
Dunedin City Council water production manager Gerard McCombie said a staff member visited the dam yesterday after a complaint and told six youths swimming at the reservoir to ''move on''.
Later in the day, a group of about 30 people, of varied ages, had gathered at the reservoir and council staff called police, Mr McCombie said.
When police arrived, only seven people remained - three older boys sunbathing on a reservoir wall and four boys diving or jumping in and swimming in the dam.
When police arrived, a 13-year-old boy was about to attempt another leap into the dam from the valve tower roof.
The boy told police he felt safer jumping into the reservoir, than climbing down from the roof, so the officers allowed him a final leap into the 8m-deep waters before giving the boys a verbal warning.
Mr McCombie said the boys jumping off the roof was a problem because the tower was a Heritage New Zealand-listed Historic Place Category 1 structure.
''If people are using it as a diving board, it will end up getting damaged, and the other issue is people can hurt themselves.''
The water level in the reservoir was lower than usual because the dam was having strengthening work.
When a new pipeline was operational the reservoir would be a back up water supply.
''We want to keep the water as clean as possible ... it's a drinking water facility ... the city provides other aquatic facilities for recreational swimming.''
