close, but a couple of points

boats can be "registered" with a state (New York, Alabama, California, Guam,
etc), and usually have to be to kept in use in that state for some period of
time. you do not need to be a US citizen to register or use a boat in any
state. mostly, you just have to pay your fees. state registration is usually
not recognized by national governments of the world.

boats can be "documented" by the US Coast Guard. There are some requirements
to this. one is the owner MUST be a US citizen (can include a US corporation).
Another is that the vessel can never be "under the command" of a non-US
citizen. (the reason for this is national defense, for if a war comes up all US
documented vessels are owned by US citizens, who presumably are loyal to the
US. This is more important with cargo vessels, but the documentation process
is the same for recreational vessels). Documentation is normally required by
other countries for a vessel to enter.

I thinks I's gettin the jist of it.
A US documented vessel belongs to a US citizen. He offers it for sale. I
buy it.
BUT
I then must turn it into an Australian vessel and because I have done so
Australia is then responsible for my actions on the high seas, not America.
The USof A doesn't want a bucketload of Aussies or any-ies rushing about the
high seas in vessels purporting to be US vessels - they reserve their
responsibilities for their citizens.

As long as I make the yacht Australian, I am then free (customs/immigration
consenting) to tour the US and any other country that allows me as an
Australian registered vessel, not a US registered vessel.
Which makes sense.

You were getting me on the finer turns of phraseology. Where you were using
'documented' I think I lost you - if I call it "registered" would that match
what you meant?

Hate to be painful but as retirement approaches this is a possibility.
Strange as it may seem, a chappie from my little country seaside town on the
other side of the world to you wandered off the the Caribbean to buy hisself
a boat to sail back because of the vast range and modest prices and it's
certainly something I'd consider.

--
Hoges in WA
Remove the zeds.