The exception to everything, though, is in the Northern Territory where absolute boating freedom reigns supreme. Here, you don’t need a boat licence – if asked, you just have to demonstrate that you have an understanding of the navigation and on-water safety framework – or even a registered boat, and there’s absolutely no limit to how large a vessel you can legally steer.
Best of all, because NT laws don’t recognise boats as vehicles, you can’t be pinged on the water for drink-driving unless there’s an on-water incident that attracts the attention of police. In theory, any resident of the Territory can read the official boat operator's handbook, then go out and buy Aussie John Symond’s 73-metre Hasna (it's for sale for a lazy $160 million, after all) and steam into Darwin with an open stubbie of beer in their hand and no one – not even police – will raise an eyebrow.
https://www.boatsales.com.au/editorial/details/how-big-a-boat-can-i-drive-in-australia-121365