A second-half penalty saw Waterford book their place in the penultimate stage of the FAI Cup following a disappointing encounter at St Colman's Park yesterday.
After a lifeless opening 45 minutes, the tie briefly came to life four minutes after the restart, with referee Joe Breen brandishing a red card and awarding a penalty.
The incident stemmed from a break on the left by Waterford's Joe Watson. He pulled the ball back to Alan Kirby, whose shot was pushed over the bar by Cobh defender Willie Byrne. Referee Breen dismissed Byrne, and Kirby slotted the ball home from the penalty spot.
The defeat will come as a disappointment to Cobh, who created the best chances over the 90 minutes. In particular, they were left to rue a glaring miss by striker Donal Golden late in the first half. Golden broke the Waterford offside trap and found himself with only goalkeeper Anthony Fennelly to beat, but he somehow contrived to shoot wide from close range.
The miss was to prove crucial. Relieved to be on level terms at half-time, Waterford soon found themselves a goal up and, with the extra man, proved too strong for Cobh for the remainder of the game.
COBH: Donegan, Kelly, Byrne, Murphy, Wolfe, Sweeney, Hughes, Clifford, Golden, Caughlan,Cregoe. Sub: McGregor for Hughes (71 mins).
WATERFORD UNITED: Fennelly, O'Brien, Frost, Reynolds, D Whittle, K Whittle, Kirby, Waters, Moroney, Watson, Rea.
Referee: J Breen, Dublin.