Abdoulaye Doucoure gave Watford a 19th-minute lead with a fine finish from just outside the area after Australia's Aaron Mooy had squandered possession.

There were few other moments of excitement until Brighton levelled 11 minutes from time, Mariappa, under no pressure, emphatically sending an Alireza Jahanbakhsh cross into his own net.

Watford remains in the relegation zone, while Brighton stays three points better off in 15th.