I agree with everything you said in your post...except the above.
I think that Natalee's body was taken off the beach and deposited out at sea. I believe this was arranged by PVDS, and this is the reason that JVDS and PVDS think they can ride this one out...knowing that the body will not be found.
I agree. This family had plenty of time to decide what to do with the body. If you lived on a small caribbean island where would you dump a body? Duh! About a mile off shore with a weight tied to her.