Ripples of Hurricane Frances left a tragic mark on a remote section of Chilmark's south shore Friday afternoon. A rip current is being blamed in the drowning death of a 58-year-old woman from Cambridge who was swimming with a friend.

Gwenneth Knight, a consultant to the Harvard University Art Museums on Indian and Islamic acquisitions, died Saturday after being airlifted to Brigham & Women's Hospital in Boston from the Martha's Vineyard Hospital.

Chilmark police said they received a call at 4:30 p.m. Friday, reporting a woman caught in a riptide on a stretch of private beach abutting the Onassis estate, where there are no lifeguards.

"The surf was phenomenal, really bad," said Chilmark beach superintendent Martina Mastromonaco. "We were at the verge of making the decision to close our beaches to swimming."

According to police and eyewitness reports, Ms. Knight and her friend Martin Hale were in waist-deep water when the powerful current swept them out.

"She was having difficulty. He was assisting her and started to become exhausted," said Chilmark police chief Tim Rich.

At that point, Mr. Hale was able to swim ashore, retrieve his cell phone and call for help, according to police.

"During that time, he lost sight of her," said Chief Rich.

It took less than 15 minutes for the first rescue workers and police to reach the beach - located more than a mile from the town-run Squibnocket beach - where Mr. Hale had then pulled Ms. Knight's body onto the sand further east toward Aquinnah.

"There couldn't have been a much more remote beach location in the town of Chilmark," said Chief Rich.

While police from both Chilmark and Aquinnah mobilized to try to save Ms. Knight, Ms. Mastromonaco, who is also the coordinator for Tri-Town Ambulance, called on her lifeguards from both Lucy Vincent and Menemsha to respond.

"We grabbed rescue reels and cans, pulling resources down to that area," Ms. Mastromonaco said.

Lifeguard Sloan Hart, who is also an emergency medical technician, ran more than a mile up the beach and began to administer CPR on the victim. The efforts paid off for a short time. EMTs reported a pulse.

Ms. Knight was taken by ambulance to the Martha's Vineyard Hospital, and then was transported to Brigham & Women's in Boston, where she died the next day.

Ms. Knight was a member of the collections committee for Islamic and later Indian art and an international fellow at the Harvard University Art Museums.

"She had a huge knowledge and traveled extensively," said her friend, Mary Rose Bolton, the director of special programs at the Harvard art museums.

"She was a brilliant woman, beautiful and very athletic," said Julie Norman, a friend of Ms. Knight's from Vineyard Haven who was on the beach when the drowning happened.

In addition to living in Cambridge, Ms. Knight also had a home on the Greek island of Hydra, said Ms. Norman.

"There's never been anyone like her," said Deborah Hale from her home in Cambridge. "She had such depth and knew enormous amounts about antiques."

Friends said she was a strong swimmer, but according to reports, the water conditions Friday and through much of the weekend were forbidding.

Ms. Mastromonaco closed the Chilmark town beaches to swimming on Sunday.

Friday's drowning comes after a difficult summer for lifeguards, who have rescued eight people from the ocean on Lucy Vincent Beach alone.

"The hard thing [about rip currents] is that they are unpredictable," said the Chilmark beach superintendent. "They change with the tides, the currents and the wind."

Ms. Mastromonaco said she posts warnings and sometimes closes the beaches to swimmers. She closed Lucy Vincent twice last week because of riptides and high surf.

Chief Rich said that swimmers along the south shore who find themselves in some trouble stand a better chance at being rescued when they are at a beach crowded with people.

"It's unfortunate this happened in this remote location," he said. "If this was Lucy Vincent, there are people and boogie boards, and they make a human chain to pull people out."

The chief said the water conditions on Friday were clearly showing the after-effects of Hurricane Frances. "The swells were unbelievable," he said.

Emergency medical technicians who tried to save Ms. Knight's life didn't return home until almost 9 p.m.

"We're a really strong core group of volunteers who worked very hard," said Ms. Mastromonaco. "We did everything we could."