Waterford enjoyed the monopoly of the scoring chances but could find no way past Bray keeper Chris O'Connor.
The 20 year old Aussie pulled off a string of top class saves in the first half to deny Waterford and leave them struggling in the relegation zone.
A free on the right by winger Colm Heffernan after just four minutes allowed defender Kevin Doherty to get in a header from close range brilliantly pushed round the post by O'Connor.
The alert Bray 'keeper again came to his side's rescue when first brilliantly blocking an effort from Blues striker Rodney Jack and then getting back to push away Heffernan's shot on the rebound at close range.
O'Connor was in the thick of the action again on eleven minutes when pushing over a powerful header by David Breen from ten yards after a clever free by Heffernan.
Waterford kept pressing forward and should really have taken the lead early in the second half only for striker Vinnie Sullivan to lob the ball over the advancing O'Connor from the edge of the box and over the top after Jack had set up the chance.
Bray showed more urgency in that second half and had their reward on 76 minutes when striker Fox grabbed the all-important goal after a long up-field clearance by O'Connor.
Fox was able to block down Doherty's attempted clearance and calmly shoot left-footed from 16 yards into the corner of the net past Holden. Bray never looked like losing that lead and comfortably held on for the three points.
Bray Wanderers - O'Connor; O'Reilly, Tresson, Roche, Keogh; Dunne, Kevin O'Brien, Caffrey, Tyrell; Fox, Kieran O'Brien (Murphy 90).
Waterford United - Holden; Breen, Doherty, Purcell, Hayes (Lyster 82); Crowley, Mulcahy, Grant, Heffernan; Jack (G.Dunphy 87), Sullivan.