Offshore sailing forces a departure from normal sleep. Most people live on a monophasic schedule. On land we go to sleep at night and wake 7-8 hours later, in an ideal world. Offshore, sailors are unable to do this and have to adopt polyphasic sleep—multiple short sleep episodes across the 24h day.

The first time I woke abruptly offshore and could not immediately understand what I was seeing, where I was or what I was doing. It was deeply unsettling. I was awake, upright, and scanning the horizon, yet my brain lagged behind reality. 

Sleep Deprivation Offshore: Why Fatigue—Not Weather—Causes Many Sailing Disasters

You may remember the redlight submarine scenes in the movie “The Hunt for Red October”. It has generally been believed that red light is the best method of protecting what we call night vision. But is this true?