A 10-month-old puppy swam more than 6 miles in the choppy waters of Lake Michigan, then walked another 12 miles to be reunited with her family in a campground after falling overboard during a family boating outing Sunday.

Edward Casas, 56, told ABC News that his son's puppy, Rylee, must have fallen overboard when he when he was in the boat's engine room trying to figure out what had caused the boat to stall. The family, visiting northern Michigan from Illinois, had been gone from the harbor at Frankfort for about 10 minutes Sunday and were headed toward the Manitou Islands when they encountered engine trouble, according to a post on UpNorthLive.com.

Kristin Casas was in the cabin with the Belgian Malinois puppy when her husband said he needed her to steer the boat while he talked on the phone with a mechanic to resolve the problem. Read More: Dogs Understand the Complexities of Human Language, Study Finds Kristin Casas told WITI-TV she noticed the Belgian Malinois puppy had joined her near the wheel to see where the boat was headed, but "my poor assumption was that she would go back to the cabin with her dad."

"Our hearts just sank," Edward Casas told ABC. "We were gone for maybe 10 minutes, and then we couldn't find her anywhere on the boat and she was nowhere to be seen in the water." The Casas family put out a "dog overboard" call on the radio. Several fishermen and the U.S. Coast Guard in Frankfort joined the search. No one found her.

Lynn Fiedor, whose husband was among the fishermen looking for Rylee, put a post on her Lost Dog Search Team and For the Louie Michigan Lost Pet Lookers Facebook pages. The Facebook groups normally concentrate on pets lost in southeast Michigan but made an exception to find Rylee.

The posts generated more than 20,000 hits. As the likes and shares soared, so did Fiedor's heart. "When I saw that, I thought, 'We are going to find the dog,'" a tearful Fiedor said.