All tender/dinghies had to be removed from all areas of the river about a year ago. Now there are 15 minute only parking bays dotted along the river for people to drop there dinghies to get out to there swing moorings.
Fines and removal are now the rules.
That said, I know one place people are getting away with it. Though I don't think it's a good idea. And surely they will crack down one day.
End of Johnson rd, Mosman park
Good luck, I wouldn't do it