i still can't wrap my mind around how perfectly capable this guy would have to have been in getting rid of a body, now that it's been well over a month, and he's been sitting in a cell. i'm just not fully convinced he's the one, or the only one anyway. (yet). i am definitely glad he's where he is.
I think, sadly, the problem here may be that there are water sources around in this case and worse still, ones that lead out fairly quickly to the sea. If you have killed and you have this option, even first time killers would choose it as it is a quick way to conceal a body, degrades the physical evidence and makes it harder for murder charges to stick. It hinders the investigation massively.
It is not a leap for someone to fantasize and plan an abduction, we know many offenders do this (many without a particular victim in mind) and then give some thought to how they will avoid detection. Especially if you have been so careless as to leave your DNA at other crime scenes. Even though that DNA is still unidentified, if police can group a few crimes together they have much more to go on to track you down.
All you can hope for is perhaps some internet searches on tides, google maps etc and maybe phone pings near the water's location. Or that something from the victim (clothing etc) eventually washes up. Shoes are fairly durable and seem to show up sometimes.
Planning to attack a victim near water might explain why an attacker would take the risk of taking a victim out of the car. Also gives an advantage of less forensic evidence of the actual attack being left in the car. I find it hard to believe that IF PR attacked Libby that he has not slipped up somewhere, we don't know what they've got.
And there are quite a few cases where areas are searched and months, even years later bodies are found there even on land. I'm not convinced all police are that great at searching, it's a difficult job sometimes. I do think they are pretty good at knowing when someone is lying and knowing when their story doesn't add up, they do that every day of the week.
As for demeanour and lifestyle of rapist/murderers, I think the thing that strikes me most about many of them, is that they are "little men". Men who are not blessed with much of anything and seek to increase their sense of power by attacking those who cannot fight back. It often flares when they are feeling a lack of control or success in the rest of their lives. Very few are obviously evil in everyday life. In prison, they are often model prisoners as attacking other men who could attack back is not their MO.