Some people are more prone to spatial disorientation than other. The source of this is the middle ear. First off I would try this, ONLY AT THE SURFACE DO NOT DESCEND, thanks. Cover your ears with plugs to prevent any water from entering you ear canal. Go snorkel AT THE SURFACE ONLY!!!!!!!! and try and prevent water from getting in your ears. If you don't get sea sick, then you have a problem wiht your ear middle or inner. Now if you do get sea sick and no water entered your ears then you have another issue which we might discuss later, but my hunch is that if you don't get water in your ears you will not get sick. The clue is that your issue is acute and not chronic you already had 100 dives and the all of a sudden...........does not add up. You might have to seek a doctor who is a pro at dive medicine. Also the best of the best get sea sick if a 300 foot cruise ship is in 50 foot seas even the captain will get sick, so what I am getting at is that if the water in your ear is the cause then you have you answer, if you get sea sick aboard the pacific princess is 10 foot seas then that is a different deal.