Hi Jessica,
Sea sickness is a common problem, which is often resistant to any anti-emetic, whether cinnarizine, betahistine or even prochlorperazine (Prescription only).
Clearly neausea and vomiting are seperate problems. So lets take a look at each in turn;
Vomiting
From your post it reads as though you actually vomited underwater. It is vitally important to avoid the inhalation of any vomitus or salt water as this will cause a very nasty pheumonia - a chemical pneumonitis. So it is important for you to take the necessary steps to prevent any contamination your regulator.
In fact vomiting underwater is uncommon. In my experience, all symptoms entirely resolve once the diver hits the water. (As an aside the army use this fact to "encourage" paratroopers to jump out of their aircraft. The appalling symptoms generated by an hour or more of low-level flying immediately disappear once you are floating on the end of a 'chute!).
Nausea is very unpleasant and results from overstimulation of the organ of balance, the labyrinth. The drugs I listed at the start of this thread often help if taken early enough. Some swear by ginger, but common sense also has a role. Sensible eating, physical fitness, fresh air, avoiding fumes from the boat engine. Some are helped by lying down with eyes closed while in others this actually makes the symptoms worse! Concentrating your vision on a distant object on the horizon may also help.
To return to your post, I am not sure if your symptoms started during or at the end of each dive. If this is the case is is highly suggestive of contaminated air, or perhaps as you suggested yourself, a viral labyrinthitis. I am assuming you are not pregnant (hyperemesis gravidarum) and have been cleared as medicall fit to dive, since a chronic middle ear condition, such as a perforated ear drum, could also be the culprit.
The commonest cure of the usual forms of motion sickness is perseverence as anxiety and hyperventilation play a part. In most these symptoms resolve in time as you become more relaxed and your brain "learns" to ignore the crazy information it is being given by the inner ear. However, some are cursed by it. The British Admiral Nelson - The victor at the Battle of Trafalgar - is said to have been sea sick every time he went to sea!
I know one madkeen diver who accepts this as normal for him, sick as a parrot on the boat but absolutely fine underwater.
Needless to say if your symtoms persist and do not fall into what we accept as motion sickness you would be wise to seek the advice of your own doctor or an ENT surgeon.
I hope this helps.
