the boat US ones to rent are NOT the kind you want. They are the ones that are meant for larger boats where you can put the EPIRB in the cabin.
They are not PLB's.
Check out this thread on 1design:
http://www.adventureonline.tv/phpBB2/viewtopic.php?t=882Basically, the preferred piece of kit that we'd used for years is now illegal. It was a nice little 121.5 mhz miniB PLB. Problem is, that unless someone was looking for you, nobody would know where you were.
Now you'll have to fork up about $600 to get a PLB that's suitable for the tybee.
Good luck! Let me know if you have any questions about the race.