Queenstown-Lakes harbourmaster Marty Black said the girl was part of a group of three or four on the Clutha River using inflatable floats about 6.30pm on Tuesday when she became trapped.
"They got swept into a tree entrapment on the upstream side of the camping ground and unfortunately one was held under for a bit and had a huge fright."
The harbourmaster said people often mistook the Clutha for being benign.
However, strong currents and trees presented danger — although this one would be removed.
"The other issue we are getting is young ones out with new toys or boats who aren’t water or river wise ... stay away from trees."
Mr Black had been left exasperated by an unthinking group which on Monday sped up the Hunter River near Lake Hawea on jet-boats.
"They spoke to a fishing game ranger who told them in no uncertain terms they weren’t allowed up there, but they politely proceeded up the river."
The three jet-boats, which included families with children, also ignored the signs warning when powered craft were prohibited.
Mr Black said they had been photographed and he hoped to issue fines.
"It’s a world-renowned fly-fishing area, it’s certainly a pretty unique waterway."
Some anglers walked 13km to reach the ideal spot to fish, and the jet-boats would have ruined things for those who put the hard graft in, he said.
Mr Black said the warm weather had meant there were many people out on the district’s lakes, but he said jet ski users needed to stop anchoring in
the water ski lanes on Lake Wanaka.
