A much-changed Waterford gave their Premier Division survival hopes a real shot in the arm and pulled Finn Harps perilously close to the quicksand.
Junior Quitirna's success from the penalty spot, two minutes into added time at the end of the first half, was one of the two defining moments of a poor game in Ballybofey.
The other, inside two minutes of the restart, saw Waterford goalkeeper Matthew Connor save a Barry McNamee penalty.
Small margins, but a huge victory for Waterford, with the Blues now within four points of Harps, who have just two wins from their last 16 outings
With half-time looming, Waterford took the lead. Jordan Mustoe, on his Harps debut, was penalised for a foul on Darragh Power and Quitirna superbly beat Mark Anthony McGinley from the spot.
Inside 30 seconds of the restart, Derek Tomney was pointing to the same spot at the Town End when Sean Boyd was taken down, but McNamee’s penalty was beaten away by Connor
The game appeared every inch one between two sides struggling at the wrong end of the standings.
A bright start to the season saw Harps win three of their first four, but they arrived here with confidence brittle.
Their cause wasn't helped when captain Dave Webster, just back in the team following a recent injury, was forced off. The Harps rearguard was already shorn the services of Shane McEleney, sidelined with an injury, and Kosovar Sadiki, suspended after an accumulation of yellow cards.
It was an opening of few chances, Boyd firing acrobatically off target when Connor’s attempted clearance didn’t get the necessary punch after Mark Coyle drilled wide.
Ryan Rainey, Webster’s replacement, was almost celebrating his first Harps goal, but his headed effort, which seemed to momentarily deceive the Waterford rearguard, was taken off the goal-line by Shane Griffin.
The game swung on the two penalties either side of Tomney’s half-time whistle.
After McNamee was denied by Connor, Harps went close again, butFoley smacked against the outside of the post.
McGinley did well to hold onto a testing try from Griffin which deflected dangerously as it made its way through a myriad of bodies.
A late Connor Barry header was as close as Harps could muster to a leveller late in the evening.
Finn Harps: Mark Anthony McGinley; David Webster (Ryan Rainey 25 (Conor Barry 83)), Ethan Boyle, Johnny Dunleavy; Mark Coyle (Ryan Connolly 83), Will Seymore; Karl O’Sullivan, Barry McNamee, Jordan Mustoe (Stephen Doherty 68); Adam Foley, Sean Boyd (Tunde Owolabi 68).
Waterford: Matthew Connor; Cameron Evans, Kyle Ferguson, Eddie Nolan, Niall O’Keefe; Darragh Power, Shane Griffin, Anthony Wordsworth, John Martin; Junior Quitirna (Cian Kavanagh 74); Prince Mutswunguma
Referee: Derek Tomney