The element of this case that has my attention at the moment is the fact AMEX says the following in it's policy:
One year wait with no body.
For someone who appears to have planned this, I find this to be the clue that something went wrong on the island. He brought snorkeling gear so I do think that he had in mind the "accidental death" to have been during that, but I don't think he would have missed this point. His former attorney stressed how careful GG was in planning things. It is a big oversight for someone with that in his character. It is a big oversight for anyone.
There is the possibility he was willing to wait a year, but from the AMEX information coming out about his phone calls to them, I don't get that.
So my theory is that his plan ran afoul, as I've covered earlier. She wasn't into the snorkeling idea. Had she been, he could have held her head under water and brought her back to shore, saying she drowned.
Combined with his attitude that he can commit crimes without getting caught, I think he improvised "on the fly" with his plan and did something else instead. Confident he could fool authorities that she was lost at sea, he disposed of the body at another location.
Would he have taken the risk to be seen at another part of the coast putting the body into the water? Or would he have just dumped her body somewhere discreet on land?
And then there is the fact no body has washed up to shore. It is difficult to establish what is fact and what is opinion about how likely it is that a body washes back to shore on that island. I welcome more feedback on that point.
Ultimately, the main thing I feel should be stressed is that without a thorough search for her on land, one cannot be certain that no body is there to be found. I feel it very well may turn up if looked for with earnest.