I think the F.B.I. was initially involved in the investigation in a limited way. While your faith in the fornsic abilities of the F.B.I. is admirable, most cases are solved not through Sherlock Holmesian ability but through the use of informants, of which there don't appear to be many in this case. Additionally, if Ms. Holloway's body was disposed of at sea, it is highly unlikely that there is any forensic evidence left to be discovered.
To call Aruba a festering cesspool because of this one incident is really inexcusable and says more about you and your fellow jingoists than it will ever say about Aruba.