Liveropol looked shaky defensively at times but Salah finished off a lightning counterattack to give the host the lead in the 38th minute at Anfield and then made sure of the victory with a cheeky backheel from a tight angle in injury time.
The win widened the gap to closest challenger Leicester even further after Brendan Rodgers' team was held to a 1-1 home draw by Norwich. The Reds have won 16 of 17 league games so far, with one draw.
“The most important thing that you have to show in this period of the season is resilience, and that's what we showed again,” Liverpool manager Jürgen Klopp said. "They had their chances, but we scored our goals.”
Liverpool entered this game as a massive favorite against the team at the bottom of the standings, but only poor finishing prevented Watford from taking at least a point in Nigel Pearson's first game in charge.
Watford striker Troy Deeney missed a chance from eight yards in the sixth minute when he went with the wrong foot in trying to convert a cross from Ismalia Sarr. Will Hughes then skimmed a shot wide with three teammates in close proximity before both Abdoulaye Doucoure and Sarr had embarrassing mis-kicks in front of goal.
Salah, though, was as clinical as ever with his second double in four days after also netting twice in the Champions League in midweek Liverpool's opener came when they broke from a corner, with Sadio Mané playing Salah through one-on-one with Kiko Femenia. The Egypt international cut back onto his right foot before curling a shot up and over Ben Foster and into the far corner.
Liverpool goalkeeper Alisson Becker then made two good saves early in the second half, one from Sarr and the other from Gerard Deulofeu, while Mané had a goal from a powerful header ruled out after VAR showed that his hip was fractionally offside.
Liverpool's injury worries deepened when Georginio Wijnaldum was forced off with an apparent hamstring problem, meaning he could miss the upcoming Club World Cup in Qatar. Liverpool defender Virgil Van Dijk nearly had an embarrassing moment 10 minutes from time when he side-footed a 20-yard back pass past Alisson and could only watch with relief as the ball trickled by the post.
Salah then made the game safe after substitute Divock Origi mishit an attempted shot on target and the ball trickled over to the Egyptian, who used his first touch to backheel it into the net. __ More AP soccer: https://apnews.com/Soccer and https://twitter.com/AP_Sports