Looking for a way to convince a significant other that an Apple Watch is a smart buy this Black Friday? One watch was the difference between life and death for kitesurfer John Zilles. After a mishap left him stranded in shark-infested water one mile off the California shore, it was the Apple Watch that allowed him to get the help he needed.

At 49 years old, Zilles had been kitesurfing for 20 years and recently learned to use a hydrofoil. While using the foil with a light wind off the coast of Ventura, Zilles had a big wipeout and the hydrofoil skated away. As he swam, the kite fell down into the water. After 20 minutes of failed attempts, Zilles was unable to get it to fly again during such calm winds. In order to get back to shore, he was going to have to swim, something that he estimated would take him two hours.

After swimming for a while, Zilles looked at his Apple Watch to check the time and remembered that it can make phone calls. Apple revealed the cellular capabilities of its Series 3 watches earlier this year. Unlike earlier models, it can work without a cellphone, using the screen as an antenna.

“I was really surprised that I had a strong signal,” Zilles told the Daily Mail. “So I called my kids, and said, ‘Don’t worry, I crashed and I’m swimming to shore, and will be home late.’ I then called my son back, and asked him to send me the number of the Coast Guard, just in case.”

To make matters worse, a great white shark nursery was discovered in the area recently. After another half hour of swimming, Zilles couldn’t stop thinking about the all the sightings. It wasn’t much longer when he kicked something hard in the water. Luckily for him, it turned out to be a part of his equipment. This still shook Zilles up enough to realize he needed help. He called up the Ventura Harbor Patrol, explained the situation, and asked for help. In just 15 minutes, the boat was able to retrieve him.

One of his big reasons for picking up the watch was to be reachable at all times and this event proved its worth. Despite the mishap, Zilles says he will continue with the sport.