My tub is too short to do the underwater thing so I wondered if you've ever tried a wash with apple cider vinegar? I've used it once or twice before as a preventative for cataracts. I thought the floaters were some kind of early cataract onset.
Also, I'm glad to hear someone else with the same theory I had: that the floaters were some kind of parasite. One of them looks parasitic but the other just looks like a reflection of my pupil.