Santiago Bueno scored and blocked a sure goal in stoppage time to secure Wolves a spot in the FA Cup fifth round in a narrow 1-0 win at a valiant Grimsby.
It was not pretty but Bueno's second-half strike was enough for the Premier League strugglers to get past their League Two opponents in less than hospitable surroundings and claim their first away win of the season.
The Mariners had beaten Manchester United in the League Cup earlier in the season and smelled more top-flight blood.
This would have been less of a scalp than their August win over United given Wolves' problems this season, and the treacherous conditions at Blundell Park were a definite leveller as the quagmire pitch made it impossible to play any
quality football.
But Wolves survived a first-half scare to gain control and put their name in the hat for the fifth-round draw.
The battling performance will please boss Rob Edwards, who is hoping a cup run can offset their inevitable relegation to the Championship.
Relentless driving rain on the east coast left the pitch resembling a mud bath, with large areas looking unplayable, but it survived two pre-match inspections.
Conditions were as alien from the Premier League as Wolves could have imagined and they almost found themselves a goal down with less than a minute on the clock.
Grimsby made headway down the left and Charles Vernam cut inside and fired an effort inches wide of Sam Johnstone's far post.
The pitch and Grimsby's physicality meant Wolves could not assert any control on proceedings.
But they almost went ahead after showing their first moment of quality in the 35th minute.
Cameron McJannet fouled Adam Armstrong on the edge of the area and Joao Gomes' curled free-kick hit the crossbar and went clear.
Grimsby were still the main aggressors, though, and had a big chance just before the break when a short corner was sent in perfectly for Tyrell Warren, but the left-back could not keep his header down.
It was Wolves who had a golden chance at the start of the second half as Mariners goalkeeper Jackson Smith scuffed his kick from a backpass straight to Armstrong, but the Wolves striker got his finish all wrong and skied it.
The top-flight side continued in the ascendancy and took the lead on the hour.
Grimsby failed to deal with a long throw and Gomes' cross was converted by Bueno's knee.
Wolves were able to keep Grimsby at arm's length and had an opportunity to extend their lead, but Tolu Arokodare fired over from a good position.
Mateus Mane also blazed over from Armstrong's lay-off as Wolves failed to kill the game.
That allowed Grimsby to push for a leveller in the final moments, but Andy Cook could not get enough on his header from close range while Bueno produced a fine last-ditch tackle to deny Tyrell Sellars-Fleming.
