I just rewatched the season finale before deleting it from my DVR and noticed something that might let Lori off the hook a bit. When Rick was confessing about killing Shane, she just looked confused until he got to the part about Carl "putting Shane down." Then
she reacted badly and looked like she was going to throw up or something.
I got the impression that she was mostly upset about the idea of Carl becoming a part of all the insane violence (especially towards a guy he'd seen as a father figure) and her own role in the sequence of events leading up to it. Then, instead of blaming herself, she blamed Rick. Not rational but in a zombie apocalypse, rationality is in short supply.
Oil rig close to the shore would be my first choice, easily defendable and immune to zombies (well except for "home-grown" ones).
The Achilles Heel of an oil rig is that it's connected to the seabed. As we know from World War Z
, zombies can walk along the bottom of the ocean (and in fact, can cross oceans) and if they stumble across one leg of the oil rig, they could try crawling up it. Not because they would know what's up there, but because in a swarm of zombies, you can count some of them to do any random thing that's possible. It's all about probabilities.
Anchors are a bad idea for a similar reason. Which may rule out ships entirely. Without an anchor, you loose control of the vessel and could run aground.