The 42-year-old, based at the city's Marionville Station, had been taking part in an exercise involving members of Lothian and Borders Fire and Rescue Service when he disappeared under the water on Friday afternoon.
Firefighters trained in under-water techniques quickly pulled him up and had to resuscitate him on the river bank.
He was then rushed to Borders General Hospital and kept in overnight.
A fire service spokeswoman said: "He was under water for such a long period of time and had actually lost consciousness.
"He had also taken in quite a bit of water so hospital staff took the decision to keep him in overnight. He was released on Saturday."
The dramatic incident happened at the Yair Bridge over the River Tweed near Clovenfords, Selkirkshire, at around 2.30pm on Friday.
Four fire appliances were already on the scene when the alarm was raised that one of the exercise team had got into difficulties.
A full accident investigation is underway to establish the cause of the incident.