Rebecca Tarbotton, an environmental activist who helped persuade big banks to stop financing mountaintop removal mining and who helped persuade Disney to reduce its use of paper made from trees cut down in rain forests, died Dec. 26 in a swimming accident in Mexico. She was 39 and lived in Oakland, Calif.

Tarbotton had been swimming in rough surf in the Pacific Ocean about a half-hour north of Puerto Vallarta while vacationing with her husband and friends and collapsed after making it back to shore, according to the Rainforest Action Network, of which she had been executive director since 2010. A coroner determined the cause as asphyxiation from water, the organization said.

The Rainforest Action Network, known as RAN, focuses on climate change and rain forest protection by challenging the practices of big corporations — a tactic it calls “environmental corporate campaigning” — rather than through legislative or legal campaigns. Although the network, which is based in San Francisco, is not as familiar a name as environmental groups like the Sierra Club or Greenpeace, it was regarded as particularly effective while Tarbotton worked there.

Tarbotton joined the network in 2007 as director of its global finance campaign. In her first years, she helped lead an effort that persuaded some major banks, including Bank of America and Wells Fargo, to stop lending money to companies that mine coal by blasting off the tops of mountains in Appalachia.

Some critics dismissed the banks’ response as public relations moves and noted that mining companies could find financing elsewhere. But other analysts said that increasing scrutiny by environmental groups was pressuring big corporations to better align their activities with public attitudes on environmental preservation.

Michael Brune, a former executive director at the network, said Tarbotton had a gift for communicating to corporate leaders how improving their environmental positions could benefit them. “Even though RAN could be confrontational, she was able to be hard on the issues but soft on the people,” he said.

Tarbotton succeeded Brune after he left in 2010 to lead the Sierra Club. Under her leadership in 2011, the network commissioned an analysis of the paper in many children’s books and determined that a large amount came from rain forests in Indonesia that were being cut down. RAN established that one of the biggest offenders was the Walt Disney Co., and the group even reported precise findings on how much rain forest wood products were used in Disney titles like “Little Einsteins: Galactic Goodnight.”

In October, Disney announced a new “paper sourcing and use policy” drafted with the help of the network in which the company said it would stop using wood products harvested from endangered forests.

Disney’s announcement included a statement by Tarbotton, who praised the company for “adding its significant voice to the growing chorus of companies demonstrating that there’s no need to sacrifice endangered forests or animals for the paper we use every day.”

Tarbotton was born on July 30, 1973, in Vancouver, British Columbia. She earned a bachelor’s degree from McGill University in Montreal and a master’s from the University of British Columbia.