[Note: If you want to find out current water quality information, head over to http://www.sdbeachinfo.com/]
I recall my first days of surfing. I was young(er than now), dumb (as much as now), and certainly had no idea what I was doing. I would go out on a closeout six foot day, paddle until exhaustion, and give up as soon as my stubborn self had reached the lineup. Literally: I'd be sitting there after 30 minutes of non-stop paddling, and just wait for the next large wave to push me back ashore.
Christmas Day of 2011, I was in the water for an early session. It wasn't bad, as the waves were nice and the lineup not crowded. I got out after a good two hours, got into the car, and drove home. There, my famished self had some lunch. Finally, I went out with friends for a Christmas dinner.
The next morning I woke up with sores in my mouth. Nothing tragic, just big pimples on the roof and sides of my mouth. They cleared up after a few days. So I thought nothing of it.
Today, I know those were surfer sores, the kind of infection you get when you decide to surf in dirty water. We get that here after a "storm," which in San Diego means any rain beyond a mere drizzle. The sewage plants and storm runoffs are typically combined, so that whenever there is atmospheric water coming down, pipe water tags along with it.