Dozens of swimmers took part in a rare sanctioned swim in the Charles River on Saturday, marking the return of the Charles River Conservancy’s annual City Splash event after a two-year pause. Participants gathered at the Fiedler Dock along the Esplanade in Boston before entering the river in groups, enjoying a 30-minute swim and the unique views of the city skyline from the water.

City Splash, organized by the Charles River Conservancy in partnership with the Massachusetts Department of Conservation and Recreation and other local organizations, drew more than 300 registrants this year. The event aims to raise awareness about ongoing efforts to improve the river’s water quality and to highlight the potential for safer, regular swimming in the Charles.

Swimming in the Charles had been prohibited since the 1950s due to severe pollution, although the river has undergone significant cleanup over the past several decades. However, the water remains unsafe for year-round swimming, largely because of the city’s antiquated sewage system, which can overflow during heavy rains, leading to elevated bacteria levels. The state currently requires a permit for swimming in the river outside of designated events.

The swim was canceled in 2022 due to elevated bacterial contamination and in 2023 because of weather conditions. Organizers conducted water testing on Thursday before the event, checking for E. coli levels, the primary indicator of water safety for swimming. Results indicated bacteria concentrations "well under" the acceptable threshold, allowing the swim to proceed.

Participants ranged from first-time swimmers, such as Carlos Villamil, who has lived in Boston for 20 years without ever entering the river, to longtime event regulars like Bill Nigreen and Kathy McDermott. Many expressed excitement about being able to swim in what they described as cleaner and more inviting water, noting the significance of reconnecting with the river.

Despite overcast skies and a drizzle in the afternoon, swimmers said the water temperature was comfortable, and enthusiasm remained high throughout the event. “It’s refreshing, even though it’s windy,” said Sarah Schendel, a first-time participant from Medford.

Organizers emphasized the importance of continued investment in infrastructure improvements to reduce pollution and enable more frequent, safer access to the river for swimmers. Laura Jasinski, executive director of the Charles River Conservancy, said the event serves as both a celebration of the river’s progress and a reminder of the work still needed to make swimming in the Charles a routine activity for Boston residents.

“City Splash is such a fun, joyful way to understand that we should be able to do this all the time,” Jasinski said. Participants echoed this sentiment, expressing hope that future conditions will allow for expanded access and more regular swimming opportunities in the Charles.