Where were you kiting? Close to the ferry or near South Melbourne Life Savers? Port Melbourne/South Melbourne isn't actually zoned for kiting (and hasn't been for a while) but they've generally turned a blind eye to it provided you stay away from swimmers and keep away from shore.
Unfortunately most of the kiters here don't actually do that meaning we won't get to do it much longer because a couple of people spoil it for the rest of us. In short, launch and then stay further offshore than the boating markers and they generally leave you alone because you're not endangering any swimmers and provided to ride slowly until you reach the boating markers, you're actually allowed to go out travel in and out to get to the boating zone. The kiting zone is a zone to allow you to stay close to shore and thereby ignore the 200m/shore 5 knot rule. The whole principle is that if you not kiting in a kiting zone you have to abide by standard boating laws which means:
1. 5 knots if you're less than 200m from shore
2. 5 knots if you're within 50m of a swimmer
transportsafety.vic.gov.au/maritime-safetyPage 49 applies to all kiters if you're in an area not demarcated as a kiting zone.