Police had not disclosed the woman's identity by late Saturday night.

Todd Zielinski of the Philadelphia Canoe Club said the 57-year-old had been a member of the group since 1989, The Philadelphia Inquirer reported. He said he is one of many members who had learned kayaking from her.

"Nobody would ever have expected this to happen to her," Zielinski said. "She's been a paddler for almost 20 years. She's paddled class-four whitewaters. A roll in flat water was a yawn for her."

The drowning was the first ever for the 100-year-old club, he said.

The woman was practicing near the club dock on the Schuylkill using a spray skirt, which covers the cockpit of the kayak. Zielinski said she apparently tucked the grab loop that would have allowed her to release the covering inside the cockpit and was thus trapped when she rolled over and did not come up again.

"It was something incredibly simple, and incredibly stupid, and it could happen to anybody," Zielinski said.