Vertigo with the sensation of rotation is called alternobaric vertigo. This occurs during a dive when one ear compensates the change of pressure before the other ear does the same. This situation, which is more common during ascent rather than during descent, is produced when the permeability from one of the two eustachian tubes is altered, meaning that this ear does not compensate properly and a relative pressure difference is created between one ear and another. .
The simptomatology is like every other vertigo: dizziness, sensation that “the room is spinning”, sometimes accompanied by nausea and vomiting, and can disappear spontaneously when you can compensate. For compensation you usually have to go back to a more shallow depth and try to avoid abrupt maneuvres of compensation since this can worsen the situation.
To avoid this you should not dive while having a cold.