Updated

Five weeks ago, Jenn Gibbons set off on 1,500-mile solo rowing journey around Lake Michigan to raise money for breast cancer survivors, blogging along the way about life on the water. Police say someone following her well-chronicled voyage from a distance may have used the information to do her harm.

A man broke in as Gibbons slept in the vessel's cabin, police say, and sexually assaulted her while the boat was moored along the shore in Michigan's Upper Peninsula. She is going public about the ordeal, hoping it helps catch the assailant and sends a message of strength to others who have been assaulted.

Her dream of traversing the lake's perimeter alone in a boat is over, but she's continuing the journey with a support team -- and partly on land.

"I don't really think it's changed me at all," she said Tuesday in a phone interview with The Associated Press, which generally does not name sexual assault victims but is doing so in this case because Gibbons wanted to be identified. "It's made more clear to me than ever that I can't let things stop me from achieving my goal."

Michigan State Police say the assault happened around 4 a.m. Sunday as the craft was moored near the village of Gulliver on the lake's northern shore.

"He somehow got on the boat. There's a hatch," Sgt. Michael Powell said. "He opened it and gained entrance."

Investigators believe the attacker, whom Gibbons did not know, may have traveled a "significant distance" after following her movements on the website, Powell said. The site tracked her progress by satellite and regularly updated her location.

The assailant, described as a man in his 30s, may have been driving a bright yellow Jeep Wrangler, police said. Its spare tire had a yellow smiley face cover. Police released an artist's sketch Wednesday. They declined to release other details, such as whether he was armed and the vessel's precise location. State Police spokeswoman Shanon Banner said the agency does not typically comment about what evidence has or has not been collected during an ongoing investigation.

Gibbons, 27, is co-founder of Recovery on Water, a Chicago rowing organization for breast cancer survivors. It's based on the idea that exercise can help prevent recurrence -- an opinion backed by the American Cancer Society in guidelines for doctors issued last April.

A native of Battle Creek, Gibbons was a member of Michigan State University's crew team, where she volunteered with a small group of breast cancer survivors. After moving to Chicago and coaching students, she formed the survivors' group in 2008. Several dozen women take part.

"It's a nontraditional support group," said Marybeth Pierce, 65, who joined four years ago. "We're not sitting around talking about the disease. We're active, we're moving."

Gibbons said she knew of no one who had circled all of Lake Michigan in a rowboat. She decided to attempt the feat, hoping to raise $150,000 to buy six new boats for the team. About $80,000 has been donated.

Her vessel, Liv, is a 19-foot custom craft designed for ocean crossings. The boat's sealed cabin provides space for sleeping and shelter during storms. It's equipped with solar panels, a satellite phone and other high-tech equipment.

Gibbons departed June 15, expecting to complete the voyage in a couple of months. She and her advisers discussed the risks of a young woman traveling solo to isolated spots along the lake, but considered rough weather a likelier threat than physical assault.

"It really makes me sad," Gibbons told the AP. "I've met so many amazing people along the way, so many generous people who want to know what I'm doing and shake my hand, people who say 'I'm a survivor' or 'my wife died of breast cancer."'

Although determined to press on, Gibbons said things would change. The boat will be towed to Muskegon, a lakeside city in southwestern Michigan. She'll bike that far, then row the final 115 miles to Chicago.

No longer will she be alone, and fewer details of her whereabouts will be made public. But she's determined to finish what she started, help the police find her assailant and heal.

"I still believe that life is a gift, even when it's scary and unfair," she wrote on her website (www.row4row.org ). "I still believe that life offers us the privilege, the opportunity, and the responsibility, to give something back, even when people try to take things away from us."

Her candor about the attack has inspired an outpouring of support in social media. Law enforcement officers, boaters and other volunteers have offered protection. She's hearing from survivors of sexual assault as well as cancer.

"This has really devastated the team," Pierce said. "She was doing it for us. It's an extraordinary gift and we're all proud of her."