Here's a dose of reality... boat theft (even the lowly jetski) is widespread and rarely investigated or any great penalties attached when someone is caught... Most jurisdictions don't even have a "boat theft investigator"... At least that was how it was back before I retired out of police work in the mid-nineties down here in paradise. Hooray when someone finally goes down but if you'll check with marine insurance outfits - they keep raising their rates as well as their requirements (mostly on bigger boats, not small skiffs particularly...) before they will even consider taking your money and writing a policy.
As for my area, south Florida... if you ever check out our local boat ramps on nice sunny afternoons you'll see not only a variety of jet skis but some really interesting young men riding them (understatement). My best guess is that no one would even consider bringing stolen jets down here - our local thieves and young gangsters have the market well covered...
One additional point.. along with young wannabe hoods on the water if you're ever near Homestead or Florida City on a Sunday afternoon - check out all the fine young men deliberately breaking every traffic rule on the books on small "home-made" scooters, mini-bikes, and four wheelers. All while the local cops are very carefully - somewhere else... One particular drive-by killing down there this past year noted that the shooter... another fine young man, no doubt, was last seen leaving the area on a four wheeler...