The remarkable rescue was captured by a CCTV camera at the back of Kayla Becerra's parents' house shortly after her dad had nipped inside for a moment.
After coming back and seeing the dogs soaked through, Kayla's dad checked the security footage and was astounded by what he found.
It shows dogs Remus and Smokey in the back yard - but something is going horribly wrong.
Kayla's dad's dog Smokey isn't the strongest swimmer and usually avoids going too deep into the pool.
However, on this occasion, Smokey had strayed out of his depth and was struggling to keep his head above the water.
Recognising what was happening to his friend, Kayla's heroic pup Remus rushed to the rescue, trying to work out a way of getting Smokey out of the water.
After attempts to pull the other pup out fail, Remus dives into the pool himself and gives his friend a boost up and out of the water.
Beaming with pride at her dog's good deed, Kayla told local papers: "Nobody was around to make sure he was doing the right thing and he still did the right thing."
The Mesa Fire and Medical Department was so impressed with Remus' actions that it decided to honour him.
"That video is so impressive to see how a dog can even go and save his friend's life," Mesa FD's Meghan Chute said. "Remus is awesome and we are so happy he was able to save his friend."
Mesa Fire Chief Mary Cameli even presented Remus with a delicious award.
"It's so important to teach your kids water safety but also it shows that Kayla [Remus' owner] did the right thing in teaching her dog water safety as well," Chief Cameli said.
"What a great day and what a happy thing for us to celebrate with Remus."
Kayla said it was "awesome" to see Remus recognised for his good deed.
She added her family was "very fortunate" that Remus was there to save the day.
Remus the hero lifeguard dog - we salute you.
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