Blue Square Bet Premier side Grimsby knocked their Football League opponents Port Vale out of the FA Cup.
Grimsby went close through Liam Hearn, who latched onto a poor header from Lee Collins but shot straight at Vale keeper Chris Martin.
Louis Dodds's strike was kept out by Town keeper James McKeown, before Sam Morsy struck the post.
Serge Makofo grabbed the Mariners' surprise winner, finding the bottom corner from the edge of the area.
Port Vale were forced to play the match in an old red Grimsby away strip because of a kit clash.
Grimsby are away to lower division opposition in Salisbury in the second round on 3 December.
VIEWS FROM THE DRESSING ROOMS.
Grimsby Town joint-manager Paul Hurst told BBC Radio Humberside:
"In my opinion it was a deserved victory. Serge Makofo is in fine form in front of goal and before he got his first goals down at Bath we looked at his record and it wasn't great, but he's on fire in front of goal and long may that continue.
"The game against Salisbury is a game in which we'll be slight favourites, but there's only one league difference and they're full-time. They've got some good players that we already know about and we'll be doing our homework on them.
"The danger is that everyone thinks we just need to go down there and turn up and we'll be in the third round. I know for a fact it won't be that easy, but we have some important league games first. "
Port Vale manager Micky Adams told BBC Radio Stoke:
"I'm bitterly disappointed and embarrassed, but that's cup football.
"I'm angry and disappointed with certain players and a little bit bewildered. As the manager, I have to take responsibility and I will do. I'm getting it wrong somewhere.
"Some of the things you see are not right, some of the body language and some of the comments I hear, but what disappoints me the most is our attitude."