When there IS a watch (as opposed to everyone being asleep at a mooring or anchor) and I know and trust the watch, I can sleep like a rock. Otherwise, I'll wake and turn over every time the wind
or tide shifts, or the moon plays behind the clouds.
There's a term coming out of PTSD research
called "hypervigilance" and it means pretty much what it sounds like. Some brains get reprogrammed, often by traumatic events
, and go into overdrive. It isn't paramoia, but rather, an increased response to stimula and enviroments that other people are ignoring.
Pretty much like the difference between "situational awareness" and "numb". You know, some people are texting and just walk into traffic, while others could never cross a curb without already having at least glanced both ways.
Shake your boots out for scorpions every morning and your bunkmates will call you crazy. Do it in the desert, and they be shaking theirs out right alongside you.