He would be wet if he immediately ran to someone the second he got out of the water, but if he was wandering around for a while wondering what happened to her and trying to figure out what to do, he would be dry by the time he spoke to anyone. It doesnt take long to dry when standing out in the sun.
Remember that there are 2 hours between the time she was last seen and he made his report, that doesn't give much time to do a crime, stash the body so well that no one can find it, and then come back. If he hadn't been to Aruba before, it is hard to see how this could be premeditated. How could he possibly plan it? That means that if there was a crime, it would have to have happened spontaneously sometime after they were last seen in apparent harmony. So, together without any apparent discord., then something happens and she ends up dead. Then he would have to hide the body so that even the locals can't find it, then he would have to stage a drowning. All in 2 hours???
The time frame just does not add up to a homicide. If he had done that you would have expected him to not report it for some time so that he would have a bigger window to clean up.
I don't buy it. This seems like just a tragic accident to me, but because of the Natalie Holloway affair, the Aruban authorities are hyper sensitive about beign seen as not pursueing things. To convince me they are going to have to come up with some real evidence, not "well, this doesnt look right".