It was a sunny mid-December day in Westfield, Ind., and the iced-over pond across the street from David Fisher’s home was starting to melt when his son rushed in from the driveway.

A large dog had fallen in the pond while chasing geese, Mr. Fisher’s 19-year-old son, Felix, said. The dog’s owners, a mother and her teenage son, were frantically trying to figure out what to do.

David Fisher, 61, a professional rope-jumping performer, scrambled to toss on a sweatshirt and a coat. When he reached the door, Felix had a new report: The teenager had fallen into the water, too.

Felix called 911.

Mr. Fisher instinctively reached for his prized possessions: two 16-foot-long cloth jump ropes, each nearly a half-inch in diameter, and knotted at both ends. Then he raced out to the pond.

The dog was somehow crawling its way to safety, Felix recalled in an interview on Sunday. But the teenager was still struggling in the frigid water some 60 feet from the shore, shouting that he was drowning, David Fisher said.