brisbane tubes

so i went to check out the brisbane tubes ( without my yak ) and there is a sign saying 'private No Boats allowed?' is this so , and is it enforced? it looks pretty damn public to me right?

True, the lagoon is posted no boats allowed. Not sure who owns it so I wouldn't mess with it.
Launch in the bay, it's all public. There's a launch at Sierra Point or paddle over from Oyster Point.