Yes i have seen videos of big wave surfing from the back of a jetski but unable to relocate the video. videos!
Its out there but very difficult to find. Guess they like to keep the footage for commercial republication.

if you own a jetski there would be a fir bit of suction and mounting going on already wouldnt there? Just kidding

we put a gopro on our jetski with the suction mount and it worked fine. We were surfing and jumping waves and all we did was tie it to apart of the steering/handle bars. I also put it on my kiteboards with a suction cup mount and tie it to my footstrap. works fine.

I just stuck the go pro to my helmet when I used one at last years IWC JP Caravan of awesomeness weeekend.

If you have a stand up, use the bar mount kit.

The main issue I can see from running the camera on the ski is you're not going to get a clear picture because of the spray, time spent with teh nose buried in a wave etc...

The only other place could work is backwards off the grab handle looking back at the person that just fell off.

I have seen them pole mounted on the back of the jetski so the view is from above and behind the driver's head, facing forwards.