Labyrinthitis is a condition of the inner ear, and therefore whether you get water in the external auditory canal or not is immaterial. However, since the essence of the illness is that the semicircular canals are feeding false information to the brain, anything that stimulates them could certainly make the symptoms worse. I can tell you from repeated personal experience that vertigo underwater is NOT fun and puts you at risk of loss of buoyancy control (mine was not due to labyrinthitis, however).
I'm a little concerned about the diagnosis, however, in view of the duration of symptoms. Labyrinthitis is most often a self-limited process which can last a couple of weeks. But at four months, I think I'd begin to worry about something else, like perhaps Meniere's disease. Did you see a family practitioner for this, or an ENT specialist? If you haven't seen an ENT doc, I'd highly recommend you do so.