Poor oral health is an important concern for athletes, as it can affect both general health and athletic performance. The aim of this study is to investigate the effects of activity in chlorinated water on oral health in elite swimmers compared to non-swimming athletes. This cross-sectional study included 101 swimmers and 100 other athletes aged 13–26 years with a minimum training intensity of five hours per week (for at least the preceding two years). Oral health was assessed using the approximal plaque index (API) and the decayed/missing/filled teeth (DMFT) index. A DIAGNOcam was used to detect caries. Results show that swimmers were younger (15 years vs. 18 years), were more likely to be female (54% vs. 17%), and had a lower body mass index (20.1 kg/m² vs. 21.9 kg/m²) and a lower juice consumption (9% vs. 24%). Non-swimmers had significantly more decayed, missing, or filled teeth due to caries and plaque. In conclusion, by comparing elite swimmers and athletes competing in different sports, we have shown that competitive swimmers have a lower incidence of dental caries and plaque. Further research is needed to test our findings and to understand this relationship in greater detail.