The new rules pertaining to systems like Sure-Path and SkiPath look complicated and confusing at first glance but are actually quite simple.
In my opinion, some of the terminology used is potentially confusing. There are two clearly defined regions where the boat path is measured for each ball. One of these regions is called “Zone” and the other is called “Buoy”. The boat path data from the “Zone” is known as “Zone Deviation” and the data from “Buoy” is known as “Buoy Deviation”.
“Zone” starts 5 meters before the boat guide and extends 10 meters past the boat guide. “Buoy” starts at the boat guide and extends 5 meters past the boat guide.
“Buoy Deviation” is the number that most accurately defines where the boat is when the skier passes the ball and is the number most commonly used by drivers for reference. This is also the number used for the “Cumulative Deviation”.
“Cumulative Deviation” is simply the sum of all “Buoy Deviations”
Lastly, there is “Gate Deviation” which is 2 meters before and after the entry gate.
What you really need to know.
For “Zone Deviation” and “Buoy Deviation” if the boat is AWAY from the skier by more than 20cm an optional reride will be awarded. The skier can improve. The score is protected.
For both “Zone Deviation” and “Buoy Deviation” if the boat is TOWARD the skier by more than 20cm a mandatory reride will be awarded. The skier can improve. The score is not protected. The skier may decide not to take a reride and accept the score that was achieved within tolerance.
If the "Entry Gate Deviation" is more than 20cm to the left or right of centerline a mandatory reride will be awarded. No protected score.
The "Cumulative Deviation" will be considered out of tolerance if it is greater than the values in the below table. Just as with Zone and Buoy if the boat is away from the skier then an optional reride will be awarded. The skier can improve. The score is protected. If the data shows the boat was toward the skier a mandatory reride will be awarded. The skier can improve. The score is not protected. The skier may decide not to take a reride and accept the score that was achieved within tolerance.
How many rerides can I get? "There shall be no more than one mandatory reride for boat path deviation in a single pass. If during the mandatory reride the boat deviation would require another mandatory reride then the score given will be the maximum score in tolerance on the reride pass. No reride. In this case the Chief Judge shall warn the driver that the driving is not acceptable, and the driver may be replaced." (official WSC text)
If the path deviation is toward the skier the reride is mandatory. If it happens a second time there will be no second reride. The skier will receive the highest score before the deviation.
If the path deviation is away from the skier there is no limit to the number of rerides per pass.
Aditional "Zone" Minutia: the “Zone Deviation” data captures the point where the boat is most toward the skier. An example of how this might be counterintuitive is if the skier is at one ball and the boat is to the left of center (away from the skier) the “Zone Deviation” number will the point where the boat is farthest to the right. Don’t let this detail hurt your brain. The rules for your reride are still dictated by deviations greater than 20cm as detailed above.
Additionally, The "Zone Deviation" data is not even displayed in the boat unless it is more than 20cm off-center.
The text above is an attempt to simplify the new rules. PLEASE refer to the official rule book for more granular information.