Four people have been flown to hospital after a jetboat flipped on Canterbury's Rakaia River.
One person had suffered serious injuries and three have moderate injuries.
Emergency services were called to the area near Double Hill shortly after 7pm yesterday.
Police said a tractor assisted in righting the jetboat.
A St John spokesperson said three helicopters attended the scene.
"Our crews assessed and treated four patients, three in a moderate condition and one in a serious condition, all airlifted to Christchurch hospital."