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Zoe83

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On my first (and only so far lol) diving trip, we went on a boat to the outer great barrier reef. it had been terrible weather since a hurricane had passed a few days before, the sea was SO choppy the boat was flying through the air for the whole way out there. EVERY passenger was seasick! lol, it probably didnt help that most of us drank the night before either. Even though everyone was sick as dogs on the boat, as soon an anyone got in the water, even witht he tight belts etc we were instantly better, diving was fantastic, but when we got back on the boat, give it 10mins and we were all sick again. same for the 2nd dive site. Why did this happen? cripples on the boat and full strength in the water..id have thought since the water was causing the sickness problem, it would have made it worse to be in it...not the case. since then whenever i feel queasy (usually from drinking lol) i try and get into some water, and it is instantly gone! can anyone give me an explanation?
 
Sea sickness is not caused by the water. It is caused by a difference between what you see, and what your inner ear experiences.

It is really motion sickness, and has nothing to do with the water per se, except as a means by which your visual and balance sensors don't match each others expectations.

Xanthro
 
Right, you're sitting on the boat, watching things move in a way your mind cannot accept, and your system rejects it. Watch the horizon. If possible, go above where there's nothing to see but the horizon.

BTW, some people get sick in the water. :sick: If you have to puke, do so thru the Reg. It's made to handle it, and this will prevent you from sucking in water.
 
I'm guessing you were on a catamaran. Doesn't cleave through the water the way a full-keeled monohull can. Bounces around in several dimensions at once instead, and really pounds down off every swell. But cats give you a lot more usable space for the same boat length, and they're terrific when motoring through shallow lagoon to the deeper water. So they're common, but so is the sickness. I was on one in May, out of Cairns, in just over thirty knots of wind. One of the crew told me they cancel the trips when it's blowing thirty-five knots.

I read an interesting explanation for sea-sickness once. The question was, what is the evolutionary benefit of a tendency toward sea-sickness? Since it's still in the genome, it must at one time have been a plus.

Well, the author reasoned that in an early gatherer society, the gatherers would encounter new plants as they radiated out across the land. Sampling a tiny bit of a new berry to check its potential as food involves risking toxic effects, the quickest of which operate on the central nervous system (typically causing disorientation and dizziness).

So if your stomach goes into "heave" mode whenever the horizon seems to be moving on you, it makes you a better new-food sampler because you can survive the bad samples by ejecting them from your stomach before they do you too much harm.

Unfortunately, sitting in the saloon of a pitching/rolling/yawing boat pretty well mimicks the effect that was selected for, so (according to the author) the once-useful response kicks in.

Fair winds and calm seas,
Bryan
 
eponym:
Since it's still in the genome, it must at one time have been a plus.

Just like the vermiform appendix. And nipples for men.


Of course, since motion sickness is an effect resulting from a cause outside of the body's control (that being the unexpected movement of liquid in the inner ear), and not an effect resulting from bodily action (which might then have tied itself to genetics), the supposition that it has an evolutionary reason is about as convincing as suggesting there is an evolutionary reason for bleeding when cut.

As people have said, Zoe83, data from your eyes and ears are used to balance you when on dry land, and also to tell you whether you are vertical, horizontal, or somewhere in between. At sea however, the movement of the boat causes your eyes and ears to send slightly different signals, so your brain cannot properly determine your position. This, coupled with its inability to predict the next movement of the boat, causes nausea.

When diving however, this problem is largely eliminated. You are in a much more stable environment, and both your ears and eyes can work together to tell your brain where you are, and, more importantly, which way up you are!

Of course, this is just a very basic explanation, and it doesn’t actually hold true for all people. Some can stand on the prow of a ship in a hectic squall and not suffer seasickness, whilst others feel queasy in a rubber dinghy on an inland lake.
 
SmokingMirror:
At sea however, the movement of the boat causes your eyes and ears to send slightly different signals, so your brain cannot properly determine your position. This, coupled with its inability to predict the next movement of the boat, causes nausea.
Hmm. And why exactly should nausea arise? Why should the stomach get involved? You aren't convincing, Mirror. Not convincing at all.

In the beginning of your post I fear you've confused morphologies with no impact on reproductive success (male nipples), therefore not selected against, with morphologies that once served a real purpose (the appendix, among other structures.) and which have not yet been selected out.

And your second paragraph just makes no sense at all. To choose an example at random, the adrenaline response (fight-or-flight reaction) is also triggered by outside stimuli. Would you argue that it can't be "tied to genetics"?

I don't claim that the theory I presented is factual, or even that it could be tested. I do think your sarcasm betrays a lack of reasoning.

Fin on,
Bryan
 
SM's second paragraph makes perfect sense. Conflicting stimuli resulting in nausea.
Vertigo, spatial misorientation. Ever done any IFR flying with numerous turns and dives?
 
The Kracken:
SM's second paragraph makes perfect sense.
I see I wasn't clear. By "second paragraph" I meant the one beginning "Of course" and ending in "bleeding when cut." That's the one I find silly.

The Kracken:
Conflicting stimuli resulting in nausea.
Vertigo, spatial misorientation. Ever done any IFR flying with numerous turns and dives?
Yes, vertigo or disorientation can cause nausea. The question I asked is why should disorientation (an inner-ear, visual thing) cause nausea? Why should the stomach get involved?

Again, I'm afraid I'm not stating my question clearly enough. To state that disorientation causes nausea is to fail to explain why it does so. Why should we toss our cookies? There's no systemic connection, other than the fact that the stomach is wired into the CNS. So is every other body part. Why does the stomach get involved?

Bryan
 
Bryan St.Germain:
I read an interesting explanation for sea-sickness once. The question was, what is the evolutionary benefit of a tendency toward sea-sickness? Since it's still in the genome, it must at one time have been a plus.

It's a common misunderstanding that a trait has to have an evolutionary benefit to survive. This is simply not true. All kinds of negative traits are in the human genome.

All a trait has to do to survive in an isolated population is not negatively affect breeding.

It is true that quite often a modern negative trait, like sickle cell anemia and diabetes have pre-modern benefits, malaria resistenace and starvation resistenace respectively, not all traits fall under this category.

I can't see how motion sickness would affect hunting and gathering. Most poisonous plant material simply tastes horrible. Those that don't, often kill you by blocking your ability to digest food. Very few attack the central nervous system.

I would guess that motion sickness is a learned response, much like the feeling you get when if you've been on a roller coaster and you watch a first person view of a roller coaster on TV, you get the same feeling. Your vision expects are certain physical response, and you can actually feel it. This does not happen to someone who has never been on a roller coaster, or gone over a hill fast.

I'll do some research on motion sickness and the post the results.

Xanthro
 
The Kracken:
SM's second paragraph makes perfect sense. Conflicting stimuli resulting in nausea.
Vertigo, spatial misorientation. Ever done any IFR flying with numerous turns and dives?
Yeah. :blinkinge :l: Thanks for the reminder.
 

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