One of the main things I would say to prevent seasickness is - always try to look at the horizon.
Only ever time I have suffered was due to me trying to kit up while on the boat while travelling in swells of 4-5ft. Spent most of the trip out looking downwards at my gear and by the time I was at the dive site, I was queasy. Next trip, had all my kit sorted before the ropes were off and had no issues at all.
People . . .it's all in your mind, and one of the prime examples of how to control a physical reaction with just your mind power. (This is
NOT as severe like the nausea/vomiting a patient would get undergoing chemo & radiation treatments for example --
you've defeated yourself & psyched yourself out already if you think you need and are dependent on such anti-nausea medication for a relatively simple condition such as sea sickness.)
Most people don't get motion sickness while driving a car or piloting a boat/plane; the reason being because you're directly effecting the action of the vessel, you see what actions you have to take to steer a clear passage, you anticipate and react to the dynamic forces that result from such actions. Your mind/body kinesthetics are synchronized, your vestibular senses unconfounded, and you don't develop the nausea associated with motion sickness.
Now short of going up to the wheelhouse and actually taking control of the boat, try sitting with the Captain at the Wheel, let him talk to you about how he's steering the boat and actually see/anticipate the resultant boat motion in response to his actions.
In other words . . .don't anticipate being seasick --anticipate being in control, knowing & feeling what the boat's motion is going to be. With practice of this simple visualization, you can even "quell the queasiness" in the roughest sea conditions --all with as little or ideally without any medication of any kind.
Again --All you gotta do is look at the horizon, see how it moves relative to the boat's motion and memorize that pattern, and then get a feeling for the rhythm of the swells and synchronize it with horizon's motion. Now when you go down belowdecks, just play it all back in your "mind's eye" as you begin to feel & anticipate the boat's apparent motion --or even imagine the boat belowdecks is transparent and you can actually see the horizon & swells in sync with the boat's apparent motion-- it's all just visualization without medication and it works!
That's the visualization technique you gotta practice, and unfortunately it's difficult to do if you're concentrating on something else like setting up your gear, reading a book, watching a video, worrying about running out of ginger pills/dramamine/bonine etc. But once you get good at it, you can hold the malaise to a reasonable level even in stormy seas --a "four" for instance on a scale from 1 to 10, with "ten" being projectile vomiting, extreme nausea, hugging the rail and begging for someone to shoot you . . . (In my thirty hour passage from mainland Costa Rica to Cocos Island, I was cognitively exhausted performing the technique over an extended period, and just simply fell asleep naturally). . .
Here's another easy beginning exercise to help develop your Cognitive/Kinesthetic Awareness and to understand the basic mechanics of it all:
Stand-up, close your eyes, and have a friend push you at random intervals from any direction around you. Try to steady yourself and resist being knocked over as best you can. After a while, you might start feeling disoriented or even dizzy & nauseous (the start of motion sickness).
Take a break . . .and then try again:
Stand-up, close your eyes, and this time have your friend at 5 second intervals push from directly in front of you, and then 5 seconds later push you coming from your right side. Repeat this set over and over --Anticipate, brace yourself and counter-react to these pushes to keep from being knocked over. You shouldn't be as disoriented as you were before because you're now in control, countering these predictable, periodic and expected forces trying to push you over.
Now apply this to being on the diveboat/LOB: you see the swells coming in a regular predictable frequency (every 12 seconds for example) --Anticipate, brace yourself and counter-react to these "pushes" to keep from being knocked over. Now close your eyes and do the same thing. At the very least, with practice (and hopefully easy rhythm swells, and non-heavy, stormy or chaotic seas to start off with!), you should be able hold off the nausea to a tolerable level.
Be patient and don't give up: it takes time, concentration & effort to develop and apply this cognitive/kinesthetic technique to the seemingly complex 3-dimensional forces acting on you at sea and achieve some relief of motion sickness symptoms . . .
the gist is to figure out and feel the rhythm of the swells and anticipate yours & the boat's resultant movement. . .
