John Bowman, 90, and Rosemary Mitchell, 65, were attacked as they paddled in an inflatable boat in Matopos National Park.
They were relaxing with a group at Mpopoma Dam, an area of natural beauty and known crocodile hotspot.
"The crocodiles attacked the air-pumped boat they were using until it punctured," Wildlife Management Authority spokesperson Tinashe Farawo said.
"Their colleagues noticed that they were struggling and drove to seek help."
When park rangers arrived both victims were still under attack and shots had to be fired to disperse the crocodiles.
The victims, who were both Zimbabwean nationals, were then taken to hospital.
Mr Bowman died before arrival, while Ms Mitchell, who had life-threatening injuries, was placed on life support.
Crocodiles are known for their characteristic "death roll" method of attack, ambushing their victim before drowning them by spinning them under the water.
Attacks are particularly common at this time of year, with hungry females leaving their nests for the first time in the three months after their young hatch.