Martin Walker, 59, had been missing for three months before the shocking find on Monday, June 24.
He vanished on March 4 and Spanish authorities immediately launched an appeal for information.
The alarm was sounded at around 1.30pm local time (12.30pm GMT) after fishermen spotted the back of a vehicle poking out of the water in the Civan reservoir.
Specialist divers dispatched to the scene found a large 4×4 around 656ft from the shore with a corpse inside.
Authorities then hauled the SUV out of the water – and through number plate identification – linked the car to the missing Brit.
Mr Walker, formerly of High Wycombe, Bucks, had been living in Zaragoza for around 15 years.
He ran Catfish Capers, a fishing tour business that operated on the River Ebro, in the Zaragoza town of Caspe, northern Spain.
The father was last seen at the Jolly Fisherman pub in the town, according to local media.
His son, Jonny Walker, told Angler’s Mail that a company vehicle had gone missing at the same time his father disappeared.
On March 15, he wrote on Facebook: “If anyone has been in contact with my dad within the last 2 weeks. Can you please contact me asap.”
Spanish authorities are yet to make a formal identification but said the body found appeared to be that of a 59-year-old male.