The Premier League's leading goalscorer made it 19 top-flight goals this season and 23 in all competitions.
Two goals from Cody Gakpo and one from Dominik Szoboszlai made it a miserable afternoon for the Tractor Boys, who scored a late consolation through Jacob Greaves.
Salah's goal moved him to seventh in the Premier League's all-time goalscorer list with 176, moving ahead of Arsenal legend Thierry Henry.
It was also his 100th goal at Anfield in the Premier League.
Deeney has previously caused a stir when he insisted that Salah was 'not world class' - but the Watford legend has never questioned the Egyptian's astonishing output.
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Deeney was shocked by the statistic that Salah has scored 20 goals or more for eight consecutive seasons.
"That's 20+ goals in eight consecutive seasons for Mo Salah," said commentator Ian Danter.
Deeney responded: "Ridiculous."
Ex-Birmingham striker Deeney previously left fans stunned by stating that while the Liverpool talisman is 'excellent', he isn't world class, adding that he'd rather tell his kids to play more like Real Madrid's Vinicius Jr.
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Salah's electric season comes as he approaches the end of his Liverpool contract.
The Egypt international has been frequently vocal about the lack of progress from the club with regards to offering him an extension - admitting recently that he is 'more out than in'.
This January window has opened up the chance for Salah to discuss his future with other clubs, as he will be a free agent in the summer.
Interest has come from the Saudi Pro League, especially from Al Hilal who are eyeing Salah as a possible replacement for Neymar.
Rumours of the move were recently stoked by Saudi sports supremo Turki Alalshikh.
Fellow Saudi Pro League side Al Ittihad made a £150million move for the Liverpool star 18 months ago, although the bid was rejected by the Premier League giants.
Salah is currently leading the Golden Boot charge in the top-flight, with Erling Haaland and Alexander Isak close behind on 17 goals each.