Sorry for the delay in responding, but was I research diving with finback, humpback and mixed sharks off MA for the past 10 days.
As regards Meniere's Disease, to the best of my knowledge it is the consensus of diving medicine experts that a bona fide diagnosis of Meniere's is an absolute contraindication to SCUBA. The unpredictable and without warning attacks of vertigo that occur with the disease simply pose too great a risk.
But, it is not at all clear that the correct diagnosis here is Meniere's as this condition almost always involves some combination of episodic, fluctuating hearing loss, vertigo, tinnitus and a sensation of fullness within the ear. When unilateral hearing loss is the sole sign or symptom, this diagnosis would not typically be applied.
Given that the diver experiences no vertigo, confusion or other symptoms worrisome for SCUBA, and the treating speSPAM -- ignoret has concluded that there "... is nothing about the problem that diving can make worse," diving would not be absolutely contraindicated.
However, there still are very important issues to be considered. These would include, but are not limited to, the inability to hear auditory alarms made by one's dive buddy, computer or the boat, and the possibility of damage to hearing in the still functioning ear. This latter concern is the reason why many ear speSPAM -- ignorets discourage diving following unilateral hearing impairment.
The decision to dive is one to be made by the individual involved after careful discussion with an ENT and consideration of the risks involved to both the diver and his companions.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.