Yeah, they have a rafting trip two or three weeks into the semester. Significantly cheaper, it costs about 20 bucks to register, a bus takes you from campus (or you can drive on your own), on a Saturday. Basically it is an excuse to drink during the day. I went and hated it (but I was sober, which was a bad plan). And it is not really "rafting" in any competitive sense. You just float, lazily, in a raft.
You do get a lot of sun, though. One thing central California is known for in the summer. I did not consider doing the trip before classes, because I had to move across the continent and get situated. I know a couple of people who are participating this year, though.