The idea of the Swiss cheese model, put forth by James T. Reason, is that there’s a number of steps between events and an undesirable outcome… multiple opportunities or defenses to avoid a poor outcome, in other words.
Each of these defenses is not 100% fool-proof—hence the holes in the cheese—but the existence of multiple defenses reduces the likelihood of poor outcomes (depicted in the image by an arrow striking a solid piece of cheese). However, if the holes of the cheese line up just right, some events can make it all the way through.
As a sailor who is keen to avoid undesirable outcomes, it’s a good model to consider.
The individual slices of cheese might be a checklist, a process, an individual’s judgment, the crew’s communication, amount of experience and practice, etc. Things that could affect the sizes of the holes in the cheese—or remove slices altogether—include taking a shortcut, cutting a corner, making decisions while fatigued or stressed, loss of situational awareness, and so on.
This is why, for example, I strive to have a reliable and repeatable anchoring process which, among other safeguards, assumes winds can reach up to 35 knots. When performed every time, the process reduces the effect that my personal state (i.e. being tired) will have on the outcome… even when the unexpected—or the unforecast—occurs.
Risk can never be completely eliminated. But tools like the Swiss cheese model can help stack the odds in your favor.
(Image by Ben Aveling, made available under the CC BY-SA 4.0 license.)