Well, I am not in Florida, but we get a few unusual things wash ashore in
Alabama as well (usually after hurricanes).  I have see Strombus gigas,
Cypraea erosa, Strombus urceus, etc.,  that collectors have found on the
beaches in  Gulf Shores.  I theorize that each of these were lost in the storm
by local souvenir shops and residents and not a natural occurrence.  One that
did baffle me was a couple of Cypraea tigris given to me by a local dive shop
owner which he claimed to have taken on a dive about 15 miles offshore.  To
his credit they did still have some meat in them and were quite ripe, but
without further confirmation I am certainly not going to add them to our
Alabama species list.
          Speaking of Caribbean species not being where you expect them, we
have taken several Caribbean species from Alabama and NW Florida waters.  Most
of these have been collected by state and federal workers conducting routine
work in the area.  Among these are included the following:  Cypraea cervus,
Cypraea cinerea, Cypraea spurca acicularis, Cypraea zebra, Cymatium femorale,
Trivia pedicularis, Tonna maculosa, Haliotis pourtalesii,  and several others.
I have vouchers of each of these.   So, my point is that even in NE Florida,
typically Caribbean species may show up naturally, but need to be carefully
documented.   I too am especially skeptical of Indo-Pacific species appearing
on American beaches.
 
Doug Shelton
Alabama Malacological Research Center
2370-G Hillcrest Road #236
Mobile, AL 36695