When Kiersten Rosenberg told her parents she would be swimming the English Channel to raise money to help a friend, they were surprised. Then they were frightened.

"When I Googled any pictures of the channel, just looking at it made me nauseous because you can't see to the other side," said her mother, Theresa Rosenberg. "My sister, who lived in Europe for many years, said 'You just can't believe that channel, how dark and wide it is.' "

The widest part of the channel, which flows between southern England and northern France, is 150 miles. For more than a century, swimmers have attempted to cross at the narrowest point: 21 miles at the Strait of Dover.

For many, the challenge of swimming the channel is a lifelong dream. For Ms. Rosenberg, a Mt. Lebanon High School graduate, the swim was a fundraiser that she and two friends undertook in honor of their friend and former teammate on the Villanova University swim team. They raised more than $4,000.

Almost two years ago, Lauren Schulman, who had been a distance swimmer on the Wildcats team, began having blurred vision and tiring easily. A diagnosis of multiple sclerosis was stunning.

Her friends gave emotional support, but they felt a sense of helplessness. A few months later, they realized they could do something: raise money for MS research -- and do it in a splashy way.

Ms. Rosenberg, Tori DeLollo and Trista Felty, who share an apartment in Philadelphia, decided to form a relay to swim the English Channel.

Unlike more conventional fundraisers, this one was daunting from the start. No one just hops into one of the world's most dangerous stretches of water without months of strenuous training, not to mention reams of paperwork.

There were rules and regulations: no wet suits, no swimming without an escort boat -- and amateurs need not apply. The women had to prove they could endure a long open-water swim before gaining authorization from the various organizations that monitor channel crossings.

They began training at pools in the Philadelphia area. But plowing through open water is vastly different, where strong currents buffet swimmers. There were other serious considerations: the currents in that part of the English Channel change direction roughly every six hours, and the water, even in summer, doesn't often get warmer than 62 degrees.

"I think I can speak for the three of us and say that we knew that the swim itself wasn't going to be the biggest challenge because we were all competitive swimmers in high school and college," said Ms. Rosenberg, a nurse who graduated from Villanova in 2006.

"It was more of the acclimating to cold water and the uncertainly of some of the factors such as how well we would deal with ocean swimming as opposed to the pool."

In the weeks leading up to the swim, they took ice-cold showers.

"You'd walk into their apartment, the air conditioning was set to about 50 ... it was freezing," Mrs. Rosenberg said.

There were other, physical dangers to consider. Jellyfish are common, ships more so. According to various channel statistics, about 600 commercial craft pass through the shipping lanes each day, with an additional 80 to 100 ferries crossing.

The three women cross-trained by swimming, lifting weights and doing cardio work. At the end of May, they swam for two hours in open water in Atlantic City as a qualifying event.

Then it was off to England.

A Channel Swimming and Piloting Federation representative joined the three to certify the attempt. Also on board were Capt. Eddie Spelling, a crew member, Miss Schulman and another friend, Clare Kubasko.

The women maintained a Web site for their fundraising attempt, www.mswim.wordpress.com, and wrote several blog posts the day before the June 29 swim.

"The water was cold, as expected, but MUCH more murky than I had thought," Ms. DeLollo wrote. "When looking underwater, you can't see past the elbow of your arm ... yikes."

They bought glow sticks to wear in the water and went to bed by 7 p.m.

Ms. Rosenberg called her parents in Mt. Lebanon around 11:30 p.m. Pittsburgh time to say they were on their way to the harbor.

After that, Mrs. Rosenberg said, it was a long, long night.

"I would doze off every now and then and think, 'Where are they?' " she said.

They were making good progress, as it turned out.

The plan was for each to swim, in turn, for an hour. Despite some initial seasickness among the group, everything went more or less as expected.

They began around 4:30 a.m. local time, but the temperature of the water turned out to be a bigger shock than anyone imagined.

"Once out of the water, I could barely move and couldn't speak because my body was so violently shivering," Ms. DeLollo wrote afterward.

The women had bought piles of fleece tops and bottoms at a Goodwill store and put them to good use.

"Lauren, along with Clare, had a system ... as soon as one of us exited [the water], they immediately had towels wrapped around us. ... Then it was off with our bathing suits and into our fleece pants and fleece sweatshirts, hats and wrapped up in blankets," Ms. Rosenberg said.

"They were also making us hot tea, broth and making sure all of us were hydrated and eating throughout the journey.

"Oh, and did I mention that this was all going on when they, too, were dealing with the boat rocking back and forth?"

One of Ms. Schulman's duties had her waving bright orange pompoms at each swimmer to let her know how much time had passed.

Halfway across the channel, they were told that, of the seven boats starting out that morning for crossings, all but two had quit.

"That made us even more excited to finish," Ms. Rosenberg said.

As she neared the end of her first hour, Ms. Rosenberg was stung by a jellyfish.

"I felt a slight tingle on my left elbow and inner arm. Then the pain intensified and I realized I had gotten stung! I screamed a little because ... it hurt a decent amount, but it actually took my mind off the cold water."

During her second swim, she was stung again, this time on the chin, but it was less painful.

Back in Mt. Lebanon, Mrs. Rosenberg called one of the other parents, who was in contact with the boat, and learned the women had passed the halfway mark. Encouraged, she went back to sleep.

Ms. Rosenberg was in the water near the end of her fourth hour when the shore of France came into view. But she hadn't reached the beach, so Ms. Felty had to jump back in, and they swam in together.

The team's official time for the crossing was 11 hours, 1 minute.

"When I climbed out of the shore of France on my last leg of the swim, I could barely stand up from exhaustion after fighting the tides of the ocean," Ms. Rosenberg said.

"I could hardly breathe and I just felt this huge rush of emotion within my body, that even now, when I think about it, makes me tear up.

"It is so hard to explain the feeling of completing something of that caliber ... but in all, it was the best, most exciting, emotional and great learning experience of my life thus far."

Sunburned and too tired to do much more than have dinner and go to bed that night, they recovered after a few days of sightseeing around England. Miss Schulman traveled back to the United States, and the others visited Germany, Italy and France.

"Having Lauren on the boat was an inspiration," Ms. Rosenberg said. "And I keep using that word because I feel that it really encompasses everything that this swim was meant to do."