Saw some guys up Geralton 2 months ago . Got towed up by a jetski to what looked like line length maybe 30m. I think the secret may be not to tow too fast and hard, a line that can handle the load, and dont drink and drive.
Unfortunatly accidents happen, so beware, we were playing around with a prarasail on a beach, a few guys running with a rope tied to the lines. Rope broke and the monkey got choked ( well almost, hit the sand flying backwards, head first)and this was only 5 m up