A total of 17 submissions on the proposal were received - all but one opposed.
Outdoor education and kayaking teacher at Wakatipu High School Ken McIntyre said allowing jet-boats in the area would put pupils at risk of collision with a jet-boat.
In his submission, Mr McIntyre said kayaking is an important part of the school's outdoor activity programme.
Pupils who kayaked on the Kawarau River from the Arrow confluence to Gibbston often referred to it ''as the highlight of their time in the programme''.
He said he was particularly concerned about the risk of collision at the Smiths Falls rapid and the section of river above, because of the higher risk of capsizing.
A submission from Central Otago Whitewater Inc, whose submission was supported by other groups, said the Kawarau Gorge was popular with kayakers from both throughout New Zealand and from overseas.
The submission said the safety measures proposed by KJet, such as having signs, cameras and spotters, would not adequately mitigate the risk posed to kayakers.
Ultimately, ''jet-boats and kayakers cannot coexist safely''.
KJet's claim that the river bed near the Smiths Falls rapid was altered in a flood in 1999, making it able to be safely navigated by jet-boats, was rejected by Central Otago Whitewater members.
A submission from Bruce Conway, of Invercargill, said he had whitewater kayaking experience in rivers around New Zealand.
Mr Conway said ''too often'' he had seen dangerous driving from commercial jet-boats in Queenstown.
He said kayakers ''doing normal paddling manoeuvres'' on the river might not be visible to a jet-boat driver or they could easily ''suddenly appear from behind a rock wall''.
AJ Hackett Bungy co-founder Henry van Asch last year told the Otago Daily Times he supported the proposed route extension. He was commenting specifically on the proposal and said it ''could push Gibbston over the edge'' and help the area over a ''hump''.
Submissions in opposition were received from the Southland Canoe Club, Otago University Canoe Club, Hutt Valley Canoe Club (in the North Island), University of Canterbury Canoe Club, Queenstown Rafting, Chard Farm, Wakatipu White Water, Whitewater NZ Inc, Otago Canoe and Kayak Club, Gary Reynolds, Riversurfing Ltd, Whitewater Canoe Club and Quentin Smith. Fish and Game is neutral for the water activity and approval of the jetty KJet wants to build near the Kawarau Bungy Centre.