Jetboats on braided rivers.

The sport is about moving your jetboat as fast as possible up/down the river, choosing the best channel, avoiding obstacles and making the best possible time for the distance.
On the Lower Waitaki, jetboat enthusiasts hold events when they can - sometimes annually, and, in the case of the "World" event, with about 4 years between contests.

Viewing the boats.

As there is no side-by-side racing on the Lower Waitaki (as there is say on the Clutha), spectators are restricted to viewing jetboats passing one-by-one as they make their way up-stream.
On the other hand, most boatees mount a webcam to capture a movie of each race-against-time and it gets onto YouTube. At the conclusion of such videos, YouTube offers a group of similar videos.

July 2013 - Otago Jetboating on the Lower Waitaki

(If the video does not show then try reloading the page. Check resolution is 360p at least, but if playback is jerky, lower the resolution to suit. Note that river flow data at Kurow varies from about 304 cumecs at 10am to about 409 cumecs at 3pm on the 6th July.)

World Jet Boat Marathon Championship 2013 - Lower Waitaki

(This video was taken on-board a helicopter. We get a good view of the braided river for a kilometer or so. A check on river flow levels at Kurow indicates flow at about 275 cumecs at 10am to about 269 cumecs at 3pm on 12th Oct. Note the number and depth of channels. Note also that few birds can be spotted - perhaps they went away earlier.)