Background Swimming is known worldwide as one of the healthiest, low-impact forms of exercise that promotes a strong body, heart, and mind. However, several studies have suggested that swimming pool chlorination is responsible for dental erosion, calculus formation, and stain in competitive and recreational swimmers, a phenomenon known as swimmer's mouth. The purpose of this observational study was to assess chlorine stain on the dentition of competitive female swimmers and divers from a university team and to determine if dental preventive practices affected chlorine stains. Methods Swimmers were recruited from the University of New Mexico Swimming and Diving Team for this IRB-approved study (#17-481). Participants completed a questionnaire regarding individual oral habits and frequency of preventive visits. Following the questionnaire, an oral screening was completed to evaluate for stain. Fisher exact tests, nonparametric Wilcoxon tests, and descriptive statistics were used to analyse the data. Additionally, a cross-sectional analysis was used to compare the chlorine stain between divers and swimmers. Results Twenty-one females, with a mean age of 20.5 years, participated in the study. One hundred percent of these subjects had staining of the teeth, despite the fact that 85% of them reported brushing their teeth 2 to 3 times per day, and 81% reported receiving regular dental prophylaxis. All participants swam 5 or more times every week, with practice length ranging from 1 to 2 hours. There were no differences in stain between collegiate swimmers and divers. Conclusion Within this study sample, extrinsic staining of the teeth was identified on all swimmers and divers and the presence of stain was not prevented by the frequency of tooth brushing or professional stain removal. Additional oral hygiene regimens should be explored to facilitate the prevention or complete removal of swimmer stain.