It is possible you have labyrinthitis or inflammation of the inner ear.
THis is caused by the viral infection or environmental allergies.
The swimming pool may make this more apparent.
Sudden onset of motion sickness without prior episodes is unlikely.
There has to be a underlying cause.
The viral infection is the most common cause.
Other causes can be high blood pressure, intolerance to the pool material, high chlorinated water ( hence chlorie intolerance) etc.
Does not sound serious.
But you should get your pool inspected as well.
Over the counter Meclizine can be tried.
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