I went and did it anyway though. I swam around in the shallow pool for a while beforehand to see if I could maybe try to breathe and swim with my face in the water, but it wasn't working. I decided to give up on that and just take the swim test anyway.
So, you jump in feet first in 10' of water (I'd never done that before, nobody told me the impact would rip my hand away from my nose...) and then swim four 25-meter lengths without stopping or hanging on the lane ropes. Only the last 25m can be backstroke, and boy was I glad when I got to that one. I'd just done something like 75m of front crawl with my head up, which I'm told is fairly inefficient.
My legs really paid for it, and I was breathing really hard, but I got it done. I went outside and barfed afterwards, then biked home. Slowly. Bleh. Cross that off the list of stupid-ass things that could keep me from graduating.