The man was caught on Tuesday after almost a week on the run, as he returned to the house he shared with the victim.
Footage of the incident went viral on social media after the incident was captured by a witness and denounced via Facebook. The attempted drowning happened last Friday, 7 April, in Oliveira de Azeméis.
The suspect, a man in his 70s, is understood to have spent time in Oliveira de Azeméis where he has a second home.
PJ police were called to investigate the case, which is being treated as attempted murder.
The crime was exposed on Facebook by a local resident who accidentally came across the disturbing incident while out walking along the bank on the opposite side of the river.
He yelled at the suspect to stop and told him he was filming the act, which deterred the man from taking his violence further.
In comments on the social media site, the witness recalled: “I was out trekking along the banks of the river when I heard cries for help, and I noticed a man trying to murder his wife by drowning her. The monster had her by the neck and was using all his force to hold her down under the water.
“If I hadn’t have been there at that moment this woman would have been murdered by this madman who has no respect for human life.”
The footage was handed over to the GNR, to be used as proof.
The woman is currently being looked after in a shelter for abuse victims. Quoting authorities, newspaper Correio da Manhã states the woman has never made a complaint against her husband and refused to do so following last Friday’s incident.