Two people have died in Queenstown Lakes district water accidents in less than a week and Mr Black is anxious to avoid any more fatalities.
Otago University student Blair Andrew Martyn (21) of Dunedin drowned while swimming alone in Lake Hawea near the Scotts beach pontoon on Tuesday and Dunedin doctor Paul Joseph Woods (29) died from injuries received in a boating accident on the Matukituki River last Friday.
Alcohol is not believed to be a factor in either accident but Mr Black said any death was "gutting".
Yesterday, Mr Black and jet-boaters hauled three young swimmers from the Clutha River near Albert Town after they got into difficulties.
Mr Black and an assistant also spent several hours yesterday afternoon stopping dozens of groups of young people from rafting the Clutha River between the Outlet and the Albert Town bridge without life jackets or paddles.
He estimated he had spoken to about 100 river users, including a few jet-boaters.
He had taken a couple of names for his "hit list" and threatened many with $500 fines.
Those people had to come back and show him they had a life jacket before being allowed back on the water, Mr Black said.
Some youths already dealt with this week had been either too drunk or poorly equipped for swimming and rafting, he said.
The Clutha River is flowing high after recent rain and in one incident yesterday, a young man who had been jumping from the Albert Town bridge got into difficulties in willows downstream of the bridge.
A second incident involved two young women who got into trouble swimming under the bridge.
One was eventually collected much further down the river, past the Hawea River confluence, by commercial jet-boat driver Brent Pihama.
Two hours after commencing patrols from both ends of the trouble stretch of water and issuing their fines and warnings to inflatable-raft users and boat users, there had been a marked improvement in behaviour, Mr Black said.
"They were just not thinking. They need to just think what they are doing. Definitely, life jackets are the order of the day. It is as simple as that," he said.
Mr Black said he would not stop young people from having fun "but they need to look out for each other and to be careful".
