It's an ocular migraine... I have those 1-6 times a year... Nothing you can do... According to my boss, sure beats having those over his "regular" migraines... Those don't give me a headache, I just can't read right for 15-20 minutes, very freaky the first time - welcome to the club.
Did it look anything like this ? (mine are a mirror image of that). Generally it's one eye only.
Now real floaters, I have those too. I now have one that's really annoying the crap out of me near the center of my eye, somedays I can get it to float away, some not, and there is nothing (appealing) you can do about those... Different deal.