Fatigue, Sleep and the 6 hr / 6 hr on/off watch schedule

Having improper sleep leads to a big increase in the risk of getting a whole range of health problems that will put you in an early grave.

The “real men” who try and withstand a lack of sleep are reducing their life expectancy so the ship owner can make more profits.

There are lots of career paths people can follow that will allow them to get as much if not more money and they will be guaranteed a proper sleep every night meaning they probably won’t die as young so will have more years to be alive enjoy their money and being with their families, the hours that some seafarers work are illegal in almost every other industry.

In the study linked in the OP it says:

In this schedule their sleep took place over an 11-hour period, and they woke up for a one- to three-hour period in the middle of the night.

That study about biphasic sleep does not support the practice of 6/6, but it does support the practice of 12/12. The participants of that study got their sleep over an 11 hour period waking up once for a short time. With 6/6 you are sleeping for 4.5 hours up for 7.5 then sleeping for 4.5 and so on… that study does not support that sleep pattern.


As a Master that does not give a fuck if my employer finds out what I think about how they are de manning tugboats at Seaspan.
I work the 6on/6off watch system and after 21 days everyone is rat bagged tired .
We all know fatigue is a major contribution to marine incidents . I am tasked with managing officers who need to work off watch either before or after they have just completed their watch .this applies to me as well .
The vessel I sail on under the manning regulations is required to carry 7
Master ,mate ,2 engineers ,2 deckhands , and a cook .
Offwatch work then is applied to myself ,mate ,and deckhands since all is required and the deckhands are always either on/off watch .
Seaspan has got a minimum manning certificate to sail with 5 crew ,take the 2 engineer and cook off .
Now imagine how this plays out with the engineer fueling ,or vessel maintenance,or repairs .
Fueling requirements are for 3 people .so now who is cooking since the onwatch deckhand is outside ,the offwatch deckhand is up for a un necessary reason .
How about when I’m off watch and doing vessel work or barge work ,a engineer must be on standby in the engine room .that should be the 2 nd engineer , but I don’t have one .
Off watch work is paid in over time at 2 x the regular rate of pay .
But that will only help you when you have saved all of the OT money in order to pay for your legal council due to a marine occurrence ,
Seaspan is required that all crew fill out a rest period sheet and fill out either the rest or work times .
My only recourse to cover my ass is once I am at home I write a email to Transport Canada ( TC) with the dates of the voyage ,area of trade ,how many crew in a letter of protest .At least this way I hope I have a chance to protect myself .
West coast companies are in a race to the bottom for crew size .the smaller crew size the better .
Less costs ,more profit .What they fail to understand is more and more officers are taking the view as I am .To cover my ass and my assets that I spent my life to achieve .
We all know more crew would be the solution.
2 extra deckhand and 1 mate so to make a crew of 10 would take all offwatch work out of the equation.
On the west coast we have hours of rest language that allows work of 16 hours in a 24 period .plus other conditions and language is included .



In my experience the STCW work/rest rules, if followed, for the most part provide sufficient rest.

I am aware that those rules don’t get followed and and I have worked on a few tugboats in Alaska. - and here.

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Sounds like this isn’t so much a 6-on/6-off schedule problem as a problem with a certain sector of tug boats. A false assumption is being made that all 6/6 operational schedules on all vessels are the same. In fact, the issue is how many days in a row you are working 6/6, and the size of the crew.

The company I work at operates Aleutian freighters. The trade has no federal work hour restrictions. Yet the 8-to-9 person crews seemingly work less hours than many 6/6 tugs. So far in 2022 work hours, averaged over an entire voyage for a boat with 6/6 watch schedule, is 11.2 hours a day (versus about 10 hours/day for a two-mate voyage).

Dutch Harbor cargo operations average less than 11 hours/day, with 13 hours off afterwards. Some individuals had to work an 18-hour day (captains) during a voyage. But the average long day (day longer than 12 hours) was 14.9 hours/day, and the average chance in any given day of working longer than 12 hours was only 15%. The average short day was 7 hours.

I’m not saying 6/6 is better than 4/8. I’m saying “6/6” as a method of describing work hours across an industry is inaccurate, because the number of days crews are working that schedule is variable between trades. A tug working 6/6 for 21-days straight with a four-man crew is seemingly a harder system that an Aleutian freighter with eight men working 6/6 for 6 days, then working breakfast to dinner for five days, etc.

If Aleutian freighters have this less-strenuous “6/6” schedule other trades are bound to also. So the term “6/6” is imprecise, as may be “4/8”.

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People who live in places where the siesta is a cultural norm do not think of biphasic sleep as “improper”.

The two watchstander system is not necessary going to result in a lack of sleep, Depending on work-load and conditions there is up to about 12 hours a day available to sleep.

This is my normal sleep schedule, even when I am home, I get up early and stay up late.

A person can have a biphasic sleeping schedule in a couple of ways. Taking afternoon naps, or “siestas,” is a traditional way of describing biphasic sleep. These are cultural norms in certain parts of the world, such as Spain and Greece.

  1. Short nap. This involves sleeping around 6 hours each night, with a 20-minute nap in the middle of the day.
  2. Long nap. One sleeps around 5 hours each night, with about a 1 to 1.5-hour nap in the middle of the day.

In many articles and in online communities, some people report that biphasic sleep schedules really work for them. Taking naps and splitting their sleeping schedule over the day helps them feel more alert and get more done.

Nobody forces me to do it, I prefer it this way.

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You’re not a spring chicken. Old folk don’t sleep as much. The obvious solution to this problem is to prohibit anyone below the age of sixty from working on tugs. :wink:

Then there’s studies like this which do not show segmented sleep is normal in hunter-gather societies:

What they found was a striking uniformity in their sleep patterns despite their geographic isolation. On average, all three groups sleep a little less than 6.5 hours a night, do not take naps and don’t go to sleep when it gets dark.

The reply to the above sleep study by a segmented sleep researcher:

Having written on the predominance of “segmented sleep” in preindustrial Europe,2 I was particularly surprised by the discovery reported by Yetish et al.1 that the members of all three of these equatorial societies did not “regularly awaken for extended periods in the middle of the night.”

In other words, the segmented sleep could be the European cultural norm but not the hunter-gatherer norm. Or perhaps non-segmented sleep is the norm for hunter-gather societies but segmented sleep becomes normal in non-nomadic society?

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The study I want to see, and will never see, to settle the issue is this:

  1. Go to an American union where the crews work 4/8.
  2. Go to another American union where crews work 6/6.
  3. Study the retirees. The ages they die. The incidence of cancer and Parkinsons.
  4. Adjust for smoking and drinking, the two largest determiners of our health outside of heredity.
  5. Figure out who lives longer and healthier.

That’s the only way to settle the issue. Demographic research. It would work well with unions because they track who is alive and dead and, to a certain degree, health patterns. They have the trust of their members (that’s an assumption on my part), so would be trusted sponsors of the research project.

I don’t see it happening, though.


There likely is a lot of self-selection going on. Most people who require 7 or 8 hours of sleep in one segment ( monophasic sleep) likely will not stay long in a situation where that is rare or impossible.

On the other hand people who can easily adapt to biphasic sleep are more likely to stay in the industry.

It’s been over 15 years since I sailed mostly standing 6/6 watches. I still sleep like I’m sailing. About 5 1/2 hours at night and a 1 to 2 hour nap in the afternoon. So far no problems…


The three-watchstander and two-watchstander system often have the same sleep pattern.

It’s very common on the three -watchstander system to get most of the sleep during one off-watch period and a short nap in the other.

Even day-workers frequently take a nap during the hour off during lunch.

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You can do this right now by going back through those Union’s monthly magazines. They always have an obituary section with the age of expiration as well as the age they retired.

Licensed is historically longer life and longer period of retirement from everything I’ve ever seen.

But your study idea sounds interesting for sure.

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This is the kind of stuff that fascinates me.

Also, do mariners live longer or shorter than the general population?

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Might be more about what they do on their time off, than what happens on the time on !! :slight_smile:



I also notice that you may be putting the cart before the horse. I mean that picking out a cultural oddball from the European Middle Ages (two sleeps during nightfall that are separated by a few hours of wakefulness) and generalizing it to be a ‘natural human condition’ might be a stretch. Considering that most peoples and cultures don’t do this today makes it hard to believe it is the natural state. Given that studies of hunter-gather societies today do not show much evidence of segmented sleep (but do show staggered sleep by age) makes it that much less believable.

Then to use that supposedly natural human condition to justify a 6/6 work schedule (which bares little resemblance to the European Middle Ages sleep schedule) is a huge stretch.

But I do agree with you that self-selection goes on in sleep tolerance and other aspects of any career.

I have no doubt in my case it’s not what I did off the ship. I’m pretty sure that working on tankers built in the 50s with asbestos everywhere and open loading and discharging of assorted carcinogens will have a greater impact. And to D.Yankee’s point, unlicensed spends more time on the ship, thus greater exposure.

No no - that was tongue in cheek - that’s what the :slight_smile: was for.

I’m not defending 6/6 watchstanding. Probably in many if not most of the cases in which it’s used additional crew members, a reduction in workload or shortened rotations is needed to reduce fatigue to an acceptable level.

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I suggest there could be better options than 6/6. One crazy idea is 14 hour on / 14 hour off. (I know it violates work/rest.) I did this during COVID on a ship that was not underway - many crew were COVID positive and locked down. With 14 hours off in a row a person can wind down, shower, sleep, wake, do stuff, nap, wake and return to work. Showing up to work four hours later than the day before is a feature that helped mitigate Groundhog Day monotony. I didn’t try 10/10 because I thought there would be pressure to sleep instead of letting sleep and waking happen naturally. I could have chosen 6/6 but fuck that. Or 12/12 but Groundhog Day sucks. The 14/14 was great but if I could do it over I would have done 13/13 for slower pseudo-time zone changes. After a few weeks the other mate and I felt well rested and alert.

Fourteen on might be rough on a busy ship while underway. But could it be worse than 6/6? I doubt it.


The two sleep phenomena is an example of two-phase sleep but the more relevant example would be the siesta.

Not claiming that it’s natural. Two-phase sleep might not fit well with modern society and the 8 hour work day but it’s not uncommon in other settings.

I suspect that humans have considerable flexibility wrt sleep schedules.

Not making any claims myself but I do think it’s helpful to have good understanding of the subject. Here’s a couple articles: