Swimming is low-impact, so there aren't many crazy impact injuries like torn ACLs or concussions. However, NCAA swimmers practice and compete year-round, which puts their joints through a major workout. Repetition injuries can befall even the best of a team's swimmers.

The most common swimming injury is swimmer's shoulder, which is a blanket term that includes rotator cuff impingement, biceps tendinitis, and shoulder instability. All of these conditions result from weakness of the rotator cuff and the muscles surrounding the shoulder blade (source).

Translation: your shoulder hurts a lot and becomes harder to move. For what it's worth, this is great training for what it's like to get old.