Pascal Gross netted to give Brighton their first home win since September after a goalkeeping howler from Heurelho Gomes.
The Austrian playmaker was allowed to turn and shoot on the edge of the box after 64 minutes but the former Spurs keeper should have saved his low shot.
The goal was also a rare highlight in a dreadful match between two sides lacking in confidence and cutting edge.
It was Brighton's first goal in 373 minutes since Glenn Murray's penalty against Liverpool on December 2 and ended a run of seven games without a win.
Chris Hughton's side, who had drawn five of their last six homes games, also celebrated a first win at the Amex Stadium since beating Newcastle on September 24.
But Watford extended their winless steak to six matches.
The Hornets avoided becoming the first Premier League team to have players sent off in four consecutive matches when referee Paul Tierney waived play on when Christian Kabasele and Tomer Hemed collided chasing a through ball before the break.
Gomes had earlier denied Connor Goldson a goal on his Premier League debut – nine months after the Brighton defender underwent heart surgery. The Watford keeper saved his 31st-minute header at the back post from a Gross corner.
Brighton level heading into the break.
Another draw at home, not damaging, but given how many times they’ve drawn already this season, they need to push for wins.
Watford looking dangerous at the AMEX, finely poised.
Silva not worried
A defiant Marco Silva insists he has no concerns over his future at Watford despite recording just one point from a possible 15.
The Hornets head into Saturday’s fixture against Brighton with four defeats from their last five outings, including a 4-1 hammering at home to Huddersfield last weekend.
After a promising start, Silva’s side have slipped to 10th in the Premier League but the Portuguese, linked to the Everton post before Sam Allardyce’s recent appointment, says he has not been hauled in front of the club’s notoriously trigger-happy owners.
Silva, who joined from Hull in the summer, is the Pozzo family’s ninth manager since their takeover at Watford five years ago. “No, of course I do not worry,” Silva said.
“I know what my job is and it is the same if I win 10 matches, you are asking me the other way. It is not a problem for me.
“I haven’t spoken to the owners. We have played 18 games and have 22 points. The last results were not what we wanted or needed, but the Premier League is not only the last three or five games.”