The Quayside, or lower river, gets very busy on nice days, especially in summer. We got there for opening, so the river was quiet on the ride out, but already getting very busy on our return trip.
Alternatively, lots of tourists give punting a go. They are the ones crashing into the banks, and annoyingly, other boats. Sometimes landing themselves in the water.
If you want to give it a try, consider renting a punt on the upper river. Though it doesn’t go through the university, it is very beautiful and much less crowded.