// By Brianna King
Seasickness is a feeling all too familiar to the regular seafarer. The onset of nausea, fatigue, lack of appetite, vomiting, and dehydration can be predetermined facts – “I will get seasick if I go on a boat” – or a case-by-case situation.
Some say that they only get sick when the conditions are somewhere in between a calm sea and terrible weather. Rough weather itself can induce seasickness. In fact, the idiom “under the weather” may have nautical origins, referring to those who become seasick during rough conditions and have gone below deck “under the weather bow”, the weather bow being the side of the ship that is getting the full brunt of the stormy weather. Others will only be sick for the first few hours, perhaps first few days, and then be totally fine. Some say it’s all psychosomatic. Seasickness is simultaneously universal and extremely personal all at once.
I am well acquainted with seasickness. Being a marine biology major, I have had many experiences out on boats, both big and very small, in both rough and calm seas. Many friends, colleagues, and acquaintances that spend time regularly out at sea admit to getting seasick. Heck, even commercial fishermen that I have met admit to being seasick at least once in their lives. Just about anyone who has experienced seasickness is immediately sympathetic. There is something forlorn and truly miserable about this state of malaise, with such an utterly simple solution: land. The most frustrating aspect of seasickness (to me) is that it is not caused by a pathogen or an injury. Seasickness simply reveals an Achilles heel in our otherwise incredible physiology – and hey, there had to be a flaw somewhere. Why does your body commit an act of such savage self-sabotage?
To truly understand seasickness, let’s dive into greater detail as to how our brain operates and perceives its surroundings. Seasickness is caused by a lack of communication between three major senses your body uses to interpret and understand the world and your physical place in it: your vision, your vestibular system (your inner ear, which maintains your balance), and proprioception.
Proprioception is considered the sense of knowing where you are, and is almost a sixth sense that you probably didn’t know you possessed. I don’t mean where you are on a map, but where you – or more accurately, parts of you – are. Imagine you’re in a sensory deprivation tank where everything is dark and you are floating in water. I bet you could touch your toes, no problem, even without seeing them, even without them touching anything else, because of proprioception. I’m sure you were hoping for something a little more exciting than that for a sixth sense – detecting magnetic fields, seeing dead people, etc. – but proprioception is important, and our lives would be incredibly difficult to navigate without it. Imagine you lost this sixth sense. If you have ever had a few too many drinks, you begin to lose your proprioception, which is the basis of field sobriety tests that police officers use to confirm whether you are intoxicated. Dr. Oliver Sacks, the late, well-known neurologist and author, described a case of a woman who had lost her proprioception in his essay The Disembodied Lady from his famous book The Man Who Mistook His Wife For A Hat. In the story, the woman loses her proprioceptive sense due to a viral infection in her spinal cord and is unable to stand unless she looks down at her feet. Her hands wander unless she watches them and she is unable to modulate the tone and volume of her voice. It is as if she is trying to control her body from outside her body; she lost the feeling of ownership or self.
Proprioception works very closely with your vestibular system – your inner ear – to maintain your balance. Your vestibular system is a series of tubes containing fluid. Looking at an image of the vestibular system, you may think that it’s a strange seashell. It’s an elegantly simple system in that, because the world is three dimensional, there are three tubes that correspond to the x (roll, moving your head side to side as if to touch your ears to your shoulders), y (pitch, moving head back to front as in nodding “yes”), and z (yaw, shaking your head as in saying “no”) axes. Here’s the thing; the vestibular just tells you which way your head is oriented. Proprioception and vision tell you the way that the rest of your body is oriented.
Back to our original question; what happens when we are seasick? Our senses that tell us where we are and keep us balanced – vision, vestibular system, and proprioceptors – get out of sync with one another. Your vision and proprioception may tell your brain that you are standing still on the boat, but your vestibular system is telling your brain that you are moving all over the place. There is a disconnect between what you perceive and what is reality. This can be exacerbated by the fact that the surface of the ocean is a featureless environment, and so your brain lacks further points of visual reference to help. The Achilles’ heel when it comes to your brain, balance, and orientation is in motion. The more unpredictable the motion, such as a windy road, a roller coaster, or the surface of the ocean, the more it thwarts your brain’s ability to determine your head and body’s orientation. But why?
Let’s take this back to our beginnings. Humans evolved in a terrestrial environment. Our bodies expect an environment in which the only movement we experience is either from self-propulsion – walking, running, crawling, etc. – or by watching other things move in relation to us. Then humans developed boats and sailing was one of the fastest modes of transportation before the combustible engine. Humans did not spend enough time on a boat to evolutionarily adapt to this environment. When we then take ourselves out of our normal environment and place ourselves on a boat, the primitive part of our brain is still expecting us to be on land because that’s all it really knows. That’s when the trouble starts. This miscommunication between your inner ear and your vision and proprioception then results in nausea – but why nausea? Why not something else, like uncontrollable singing, or temporary blindness, or something more benign like a stuffy nose?