nothing too major. everything was fine on the surface then we began to descend as a group. The first breath that I took underwater I got a mouth full of water...not air. I kicked right back to the surface immediately. I tried it again....just water. I tried my secondary source and it worked fine.
My buddy met me at the surface and I told him what was going on. He descended to the 24 foot deck where we were all to meet just below me to inform the instructor that I was having difficulty. In the meantime I was hitting the purge button and generally knocking the side of the regulator to see if I could get it "un-stuck".
Finally the instructor surfaced and just as he did my regulator began working again. He figured I had some sand or something in there and that all would be fine. He told me that we should get going to catch up with the rest of the class who had continued on with the dive con.
I was a little uncomfortable and not trusting my regulator all that much but I continued anyway. Looking back, I shouldn't have, even though I didn't have trouble the rest of the dive. And the instructor shouldn't have assumed anything either, but that's a different topic.
In the meantime, the group that had gone on without me and the instructor had gotten split up accidentally. Problems ensued with one of the divers that wasn't doing well in the class as she got lost on her own for about 5 minutes. We learned all of this after the dive was over. Needless to say, that final dive of the weekend was one to forget for the whole class. Luckily everyone ended up making out ok.