Swimmers were scheduled to take their annual dive into Boston's Charles River on Sunday. But due to elevated bacteria levels, the event dubbed "City Splash" has been canceled.

Organizers had already delayed the event due to the elevated bacteria, which was caused by recent heavy rains.

The Charles River Conservancy, which organizes the event, hopes to reschedule for later this summer or potentially even in the fall.

"The amount of rainfall experienced this week elevated bacterial counts above acceptable swimming standards, as reflected in water analysis results we received Friday and Saturday. While cancelling the event is disappointing, our top priority is swimmer health and safety," organizers said in a statement.

According to the Charles River Conservancy, the event's popularity this year was eye-opening for future planning. Last year, more than 300 people swam in the river during City Splash. This year, even more people were signed up before the event was canceled.

"With close to 400 swimmers registered, this year's event planning was also an overwhelming showing of the need and desire to make more swimming spaces available," organizers said.

City Splash is designed to raise awareness and bring river swimming back in Boston. It is a state-sanctioned swim in what has been named one of the cleanest urban rivers in the United States.

The event takes place near Fiedler Dock on the Esplanade. Swimming in the Charles River is only allowed with a permit from the Department of Conservation and Recreation.

Though the Charles River Conservancy says it has a vision for a swimmable Charles River, they add that the group "does not encourage swimming in the Charles outside of permitted events."