There is new info coming out all the time regarding fatigue and what it does to the body and brain, latest being that fatigue (related to sleep deprivation) actually destroys certain types of brain cells in a mechanism similar to dementia.
I just finished a hitch with a six on, six off schedule the last week or so, and even that brief stint of sleep disruption was fucking me up enough to make a couple of dimwitted mistakes here and there. 20 hour work days are deadly (as we see in the case of this tug). Never discount fatigue in a casualty analysis. It really is like being drunk