Swansea City staged a remarkable late fightback to beat Watford and give Carlos Carvalhal victory in his first game in charge of the Welsh side, lifting them off the bottom of the table.
In a lively start to the match, Jordan Ayew struck the bar from 25 yards for the visitors before Andre Carrillo headed Watford in front on 11 minutes.
Neither side seized control of the match in a disjointed second half and, as the nervous hosts retreated with five minutes left, Swans substitute Oli McBurnie nodded down for Ayew to convert from close range.
In the 89th minute, Heurelho Gomes saved a powerful effort from Nathan Dyer but could only push it into the path of another Swansea substitute, Luciano Narsingh, who finished well to spark ecstatic celebrations in the dugout and the away end.
Just a fourth win from 21 Premier League games this season sees Carvalhal’s side overtake West Brom, who are now at the foot of the table, and moves them within two points of safety.
For Watford, a fifth defeat from six league matches sees them stay in 10th place.
Carvalhal’s dramatic start
There was an element of surprise to Carvalhal’s appointment, coming as it did just days after he was dismissed by Sheffield Wednesday with the Owls 15th in the Championship table.
However, the Portuguese’s penchant for attractive football was in keeping with the Swans’ ethos of previous years – and it was evident in the early stages at Vicarage Road, one crisp passing move ending with a rasping 25-yard shot from Ayew which hit the bar.
Despite that promise, the fragility of the Swansea players’ confidence was exposed by the opening goal as their static defence allowed Richarlison through to fire a shot which Lukasz Fabianski could only push towards Carrillo for a simple close-range header.
The visitors’ heads dropped from that point, the recalled Renato Sanches cutting a frustrated figure as he and his midfield team-mates struggled to find a balance in their flat 4-4-2 formation.
Carvalhal brought on winger Narsingh as well as Nathan Dyer and young striker Oli McBurnie – for Roque Mesa and Tammy Abraham, who had both disappointed – in an effort to rejuvenate his side, and it proved an inspired move.
Watford surrendered the initiative in the closing stages of the match and Swansea appeared to feed off their opponents’ nerves.
McBurnie showed great composure to head the ball down to Ayew, who volleyed in the equaliser with four minutes left to send the travelling supporters into raptures.
And to the disbelief of many at Vicarage Road, the Swans struck again three minutes later, Narsingh’s late goal breathing new life into the Welsh side’s bid for survival and marking a dramatic start to Carvalhal’s reign.
Watford let it slip
Watford had ended a run of four successive defeats when they beat Leicester on Boxing Day, and their energetic start against Swansea suggested Marco Silva’s side were rediscovering some of the form which took them within three points of the Champions League spots earlier this season.
Richarlison tormented Swansea’s defenders when he drifted infield from the left wing, while Abdoulaye Doucoure was central to the Hornets’ efforts to outmuscle their meek opponents in midfield.
The home side had chances to extend their lead, with Richarlison seeing a header saved by Fabianski and Molla Wague having a goal disallowed after pushing Tammy Abraham at a corner.
Swansea seemed there for the taking at times but Watford failed to take advantage, allowing the game to pass them by as time wore on, inviting pressure.
It proved to be costly as a hitherto toothless Swans side appeared emboldened by their opponents’ inability to kill the game off and, after Ayew struck the equaliser, Watford only had themselves to blame as Narsingh latched on to Gomes’ save from Dyer.
Man of the match – Oli McBurnie (Swansea City)
‘We had to kill the game’
Watford boss Marco Silva speaking to Match of the Day: “It’s really hard to take. We are disappointed, our fans are as well.
“We did enough to win the match. We controlled the match. They had one shot off the bar but we controlled the match, scored one goal and had more chances to kill the match, even seconds before the goal.
“At this level, when you don’t score, it gives them belief. One cross after, they score one goal and it looks a bit offside. Even with 1-1 we need to be different, to keep focus to the end.
“We did enough to win. We need to kill the match and that is a gift for them. We created enough chances to comfortably win this match.”
Swansea manager Carlos Carvalhal speaking to Match of the Day: “We tried everything to win. Watford are very strong. We felt a little lucky in moments, but Watford were lucky also.
“The game is like this, but we prepared very well, changed the formation and had just two training sessions with the team.
“I must give congratulations to my players. They are better players than they are showing. They need a plan and a dynamic. During the game they were better and better.”
Watford travel to Premier League leaders Manchester City on Tuesday (kick-off, 20:00 GMT), while Swansea host Tottenham (19:45).
Match ends, Watford 1, Swansea City 2.
Second Half ends, Watford 1, Swansea City 2.
Tom Cleverley (Watford) wins a free kick in the defensive half.
Foul by Oliver McBurnie (Swansea City).
Corner, Swansea City. Conceded by Roberto Pereyra.
Corner, Swansea City. Conceded by Tom Cleverley.
Corner, Swansea City. Conceded by Christian Kabasele.
Attempt missed. Abdoulaye Doucouré (Watford) right footed shot from outside the box is high and wide to the left. Assisted by Andre Gray.
Goal! Watford 1, Swansea City 2. Luciano Narsingh (Swansea City) left footed shot from the centre of the box to the bottom left corner following a set piece situation.
Attempt saved. Nathan Dyer (Swansea City) right footed shot from outside the box is saved in the centre of the goal. Assisted by Luciano Narsingh.
Marvin Zeegelaar (Watford) is shown the yellow card for a bad foul.
Foul by Marvin Zeegelaar (Watford).
Jordan Ayew (Swansea City) wins a free kick on the right wing.
Goal! Watford 1, Swansea City 1. Jordan Ayew (Swansea City) right footed shot from the centre of the box to the bottom left corner. Assisted by Oliver McBurnie with a headed pass.
Attempt saved. Andre Gray (Watford) right footed shot from the centre of the box is saved in the centre of the goal. Assisted by Roberto Pereyra with a through ball.
Corner, Swansea City. Conceded by Marvin Zeegelaar.
Substitution, Watford. Roberto Pereyra replaces André Carrillo.
Sebastian Prödl (Watford) is shown the yellow card for a bad foul.
Foul by Sebastian Prödl (Watford).
Nathan Dyer (Swansea City) wins a free kick on the left wing.
Attempt blocked. Abdoulaye Doucouré (Watford) left footed shot from the centre of the box is blocked. Assisted by Richarlison with a cross.
Substitution, Swansea City. Nathan Dyer replaces Sam Clucas.
Abdoulaye Doucouré (Watford) is shown the yellow card.
Abdoulaye Doucouré (Watford) wins a free kick in the defensive half.
Foul by Jordan Ayew (Swansea City).
Attempt missed. Jordan Ayew (Swansea City) right footed shot from outside the box is high and wide to the right. Assisted by Tom Carroll.
Substitution, Watford. Andre Gray replaces Stefano Okaka.
Offside, Watford. Tom Cleverley tries a through ball, but Sebastian Prödl is caught offside.
Richarlison (Watford) wins a free kick on the left wing.
Foul by Kyle Naughton (Swansea City).
André Carrillo (Watford) wins a free kick on the right wing.
Foul by Martin Olsson (Swansea City).
Foul by Daryl Janmaat (Watford).
Renato Sanches (Swansea City) wins a free kick in the defensive half.
Ben Watson (Watford) wins a free kick in the attacking half.
Foul by Tom Carroll (Swansea City).
Offside, Swansea City. Oliver McBurnie tries a through ball, but Luciano Narsingh is caught offside.
André Carrillo (Watford) wins a free kick on the left wing.
Foul by Oliver McBurnie (Swansea City).
Offside, Watford. Stefano Okaka tries a through ball, but Abdoulaye Doucouré is caught offside.