The 27-year-old has previously been a target for Newcastle United and Norwich City in reason years but it is understood that Watford are now looking to sign the Dutch left-back.
Marco Silva's side are going through somewhat of a left-back crisis at the moment and it is an area the coach is keen to address. Jose Holebas, the only recognised senior left-back in the squad, was suspended for his side's clash with Brighton last Saturday and Miguel Britos, who filled in for Holebas, was himself sent off during the game.
The Hertfordshire club have made an impressive start under new boss Marco Silva, picking up five points from their opening three Premier League games.