I'm not sure this is true. Florida doesn't have jurisdiction over what a Florida resident owns in a foreign country, including boats.
The requirement is not on the property it's on the resident. If you become a resident of Florida you have 10 days to register your vehicles in the state. If you are a Florida resident and buy a boat in another state or country you owe Florida sales/use tax on that boat even if you never bring it into the state unless you can show you paid an equivalent tax in another US state. There is a provision for non-Florida residents that have owned the boat in another US taxing jurisdiction for more than 6 months being exempt, but there is no exemption for a Florida resident. It is a requirement of residency. As a resident you are under their jurisdiction even if the vehicle/vessel is not.
You are mixing immigration with customs
. Vessels aren't 'tourists', they are foreign flagged vessels with permission to be in US under a set of rules. Owner can be a foreigner or US citizen.
Technically you are correct they are not tourists but it is basically treated as a visiting vessel. If you become a resident of the state you are no longer visiting and the 10 day rule
above applies. It may be foreign flagged, and probably can remain so, but it will need a Florida registration
sticker just like a US documented vessel rather than a state titled vessel. It is getting the state sticker that triggers the tax man. In this case, where the resident and the vessel are both actually in the state there is no question of jurisdiction.
I know of a US citizen that owns a corporation in BVI. The corp owns the vessel and it's been here in the US under a US Customs
for years. Nothing illegal about it.
This true, because the vessel is owned by a corporation, not an individual and you are of course talking federal law. Under Florida law if he is the sole stockholder in the corporation he might technically owe the tax anyway. I know it works that way for corporations based in tax haven states like Delaware. With foreign corporations the state may not be able to find out who the stockholders are, effectively shielding the owner from the tax requirement. If he is a resident of another state the laws may be different.
Again, this happens all the time. If a foreigner owns a car in Florida, most insurance
companies require a Florida Drivers License. Florida issues the license to match the term of the visa, i.e. 6 months if they are under the visa waiver program. There is nothing illegal, nor frowned upon, when a foreigner shows a valid Florida Driver's License and owns a foreign vessel.