I was down at St Kilda on Wednesday for a session and was amazed at the size of those signs. One of them is pretty much on a direct tack for a beginner's first stand up session. It's only a matter of time before some poor beginner wraps their kite around one of these signs. Really poor choice of marker for kiting.

If you look at the Parks Vic boating update you'll see that those markers are the ones to indicate the 5-knot zones and no boating zones.
There is quite a large 5-knot zone down by the slipway at the yacht club which is shown in the updated zoning plans. There is also quite a large 5-knot zone around where the boats are moored and right up to the end of the breakwater.

To be honest there needs to be a bit of a reality check as to how stringently these are enforced. If 'they' choose to be asshats about it then there'll be a lot of annoyed kiters at St Kilda. If 'they' choose to use these buoys as a way to reel in the idiotic clowns who just blatantly ignore common safe kiting guidelines - then good for them.

There's also been a large chunk taken out of the currently used kiting zone at Altona.
FYI, anything to the pier side of the new rock groyne they've installed is a 5-knot zone so you shouldn't be kiting there.

http://www.parkweb.vic.gov.au/3zones.cfm
All info available from the Parks Vic website.