The dog's owner Michael Robinson told 7NEWS his 3½-year-old Dogo Argentino named Gladiator Maximus ("Max" for short) chased a coyote across the reservoir and both fell into the icy water about 5 p.m.

Robinson said Max outlasted the coyote as they tread water in the icy lake. The coyote went under but Max kept paddling to stay afloat.

West Metro firefighters arrived and one of them suited up in a special protective cold-water rescue suit and crawled on the ice to the center of the reservoir where Max was struggling in a small open area of water.

After the firefighter grabbed the dog, the two were pulled to safety by other firefighters.

"It was a tense moment for me," Robinson told 7NEWS.

Onlookers didn't know how long Max would last in the frigid water.

"He'd been in the water for 20 minutes just swimmin', swimmin' and he still had the energy -- forget the energy to walk, just the fact that he was still alive when they got there ... then to walk all the way back across the lake and up the bank, down the other side to get into the paramedic van," Robinson said.

Robinson said Max acted like the rescue was no big deal.

"He walks off, looks back at the diver, almost like a thank you. He stands there and looks to see where I'm at and walks right on off into the wild blue," Robinson said.

Max and Robinson, who had been out in the cold waiting for someone to save his dog, were warmed up in an ambulance and taken back to their nearby apartment.

He applauded West Metro firefighters for their efforts in saving Max.

"We’re blessed to have him here tonight," Robinson said, adding that Max is doing well.

"We gave him a big bone to chew on and his body temperature is back up and he's back up and running and jumping around the house."

A Dogo Argentino is a hunting breed but Robinson said Max will be on a hunting timeout for a while.