They say a dog is a man's best friend, but to John Unger, a Wisconsin resident, his dog, Schoep, means everything.

Unger adopted Schoep, named after the famous Wisconsin ice cream, when he was just a puppy, and the two have been together ever since. Now, at 19 years old, Schoep has arthritis and has trouble sleeping, the Pioneer Press reports. Unger found that water is therapeutic for his pained buddy, so he takes Schoep into Lake Superior and lulls him to sleep.

Photographer Hannah Stonehouse Hudson, owner of Stonehouse Photography and a friend of Unger's, decided to capture the relationship between the man and his dog down by the water.

"This photo was from a last minute session," the Bayfield, Wis., photographer told The Huffington Post in an email. "We had been trying to get together for weeks, but it kept not happening because of my travel schedule for Stonehouse. We finally got together last Tuesday (the 31st). I had about 5 minutes to shoot and this is what I caught -- a man and his dog. John loving his Schoep, and Schoep trusting John so much he falls asleep in the buoyancy of the water. This is in no way posed. I hate posed photos. They never, ever capture the true essence of anything."

Stonehouse Hudson decided to post the photo to Facebook, where she described the pair's loving relationship.

"This 19 year old Shep being cradled in his father's arms last night in Lake Superior," she wrote in the Facebook post, which has received more than 207,000 likes and 116,000 shares as of Wednesday morning.

"Shep falls asleep every night when he is carried into the lake. The buoyancy of the water soothes his arthritic bones. Lake Superior is very warm right now, so the temp of the water is perfect. I was so happy I got to capture this moment for John. By the way, John rescued Shep as an 8 month old puppy, and he's been by his side through many adventures," she continued.

Stonehouse Hudson never imagined the tender moment she captured would eventually go viral and touch the hearts of hundreds of thousands.

"John lives for this dog, and for the dog's comfort," she told HuffPost. "My mother has a saying, 'Everything is for the comfort and convenience of the Dog.' John is a prime example of this."

Stonehouse Hudson regularly photographs dogs as part of her profession. She offers pet sessions and often takes pictures of dogs at weddings. To give back, she does free shoots of hard-to-place animals for local shelters.

She said the photograph of Unger and Schoep is more than just a moment frozen in time; it's an everlasting reminder.

"I want people to identify with this photo, and remember a time when they felt safe, loved, and cared for," Stonehouse Hudson said. "Then I want them to channel those feelings and pay it forward! There is way too much negativity in this world - maybe with this one photo we can start to change things just a tiny bit."

UPDATE: John Lundy of the Duluth News Tribune interviewed John Unger, who described how Schoep saved his life. After breaking up with his former fiancee, Unger had been having suicidal thoughts. “To be honest with you, I don’t think I’d be here if I didn’t have Schoep with me (that night)," Unger told Lundy. "He just snapped me out of it. I don’t know how to explain it. He just snapped me out of it. … I just want to do whatever I can for this dog because he basically saved my ass.” Minnesota Public Radio reports that the popularity of the photo has spurred an outpouring of support in the form of donations to help pay for laser treatment for Schoep's arthritis.

LOOK: John Unger cradling his dog, Schoep, in Lake Superior.

