But the ACLU and Frankel's family and friends confirmed his death.
Yesterday, Chirls said that he accompanied Frankel's brothers to the D.C. Medical Examiner's Office to identify his body.
"We were told there were no signs of trauma or injury that would be consistent with a crime or a fall," Chirls said. "What they found was consistent with death from natural causes while out running."
The D.C. Medical Examiner's Office declined to comment.
Chirls said that Frankel was found 20 feet from a running trail in jogging clothes and - without offering specifics - that he had been experiencing medical symptoms the previous morning that were consistent with the preliminary finding.
So far, though, there is no indication as to how Frankel ended up in the water, Chirls said.
Frankel and Chirls met when both were law students at the University of California at Berkeley, the same school that Frankel, a Burbank, Calif., native, attended as an undergraduate.
Following graduation, the couple moved to Philadelphia. Frankel worked as an associate at a law firm before founding his own practice, where he worked in criminal, civil and security law.
In 1992, Frankel quit his practice to become legislative director of the ACLU of Pennsylvania.
"When he became a lobbyist he found his real calling," Chirls said. "He knew that getting something done in a collaborative body like a legislature wasn't a matter of pushing people around but of persuading and working together."
Karl Baker, a member of both the Philadelphia and state ACLU boards, remembered Frankel's ability to search out people from different backgrounds and appeal to their common rationalities.
"People trusted him because he was not the typical paid lobbyist," Baker said. "He didn't have funds to take them out to lunch. The only thing he had to offer was common sense, and people appreciated that, whether they agreed with him or not."
Jeff Hunsicker, state counsel and lobbyist for the Service Employees International Union, agreed, noting that Frankel built coalitions that had never before existed.
"When you think about labor unions you don't think of them working with the ACLU, but Larry built that connection," he said. "There were a lot of people he brought together to fight for human rights and that will be part of his legacy - the fact that he's brought a wide range of people to work together on common issues that we all care about."
Frankel did such a good job as legislative director that from 1996 to 2001 he was chosen to serve as the executive director of the ACLU of Pennsylvania, a promotion that was "an honor to his talents" but did not honor the ambitions in his heart, said Burton Caine, a longtime member of the state ACLU board and a law professor at Temple University.
"He didn't want to prepare budgets - he wanted to be in the field fighting," Caine said. "He had a great effect there because people knew him, they trusted him and he could stop something before it festered into a sore."
Thus, Frankel decided to step aside as executive director in 2001 and return to his role as legislative director.
In 2003, Frankel and Chirls, who would go on in 2005 to serve as chancellor of the Philadelphia Bar Association, affirmed their partnership in a commitment ceremony in Yardley.
Chirls declined to comment on the status of his relationship with Frankel, except to say that they were longtime partners, "until recently."
In 2008, Frankel accepted his current position as counsel for the ACLU's Washington legislative office in D.C., where he assisted ACLU affiliates in every state in developing their ability to lobby at the local level.
In his spare time, Frankel was a "voracious reader" who loved Jewish- and Spanish-history novels. He also enjoyed Spanish culture, the outdoors and wildlife, Chirls said.
Frankel is survived by his father, two brothers, a sister, three nephews and a niece.
Funeral arrangements were pending.