I'll second (or third) the recommendation for freedive. I used to have trouble clearing my right ear, and for a while I wondered if I were anatomically unsuited for SCUBA. I took freediving and learned (and practiced a lot) clearing techniques (like Frenzel), and now have zero issues with clearing.
I know that's not your issue, but freediving gets you comfortable with having your face in the water (static apnea) and just going without air for long periods of time. The natural human instinct is to panic within seconds of having your air cut off, or the prospect of having it replaced with water. In free diving, you learn to suppress this natural reflex, which translates into a much higher threshold for panic when something goes amiss in SCUBA.
I know that's not your issue, but freediving gets you comfortable with having your face in the water (static apnea) and just going without air for long periods of time. The natural human instinct is to panic within seconds of having your air cut off, or the prospect of having it replaced with water. In free diving, you learn to suppress this natural reflex, which translates into a much higher threshold for panic when something goes amiss in SCUBA.