Town’s unbeaten run continued but they were held to a draw by Altrincham at Moss Lane.
The Mariners looked to be on course for six league victories in a row when Nathan Arnold’s second-half strike gave them the lead.
But the hosts regrouped and they levelled through defender Scott Leather in the last minute.
Altrincham had started well but Town grew into the game and created the better chances before half-time.
That pattern continued after the break and Arnold’s goal on 67 minutes seemed likely to be enough for all three points.
The home side had other ideas though and after a late spell of pressure, they got their rewards to claim a point.
Town boss Paul Hurst named an unchanged starting XI after Tuesday’s home victory over FC Halifax Town.
That meant Carl Magnay was fit to keep his place at right-back after coming off during the second half against the Shaymen.
He lined up as part of a defence which also included Toto Nsiala, Shaun Pearson and Aswad Thomas, in front of keeper James McKeown.
Arnold, Craig Disley, Daniel Parslow, Harry Pell and Scott Neilson were the midfielders, with Lenell John-Lewis leading the line in attack.
The Grimsby bench was also unchanged, with Scott Brown, Jack Mackreth, Ross Hannah, Craig Clay and Jon-Paul Pittman all awaiting their chance to go on as substitutes.
Altrincham were three points and three places above the relegation zone at kick-off and would be aiming to climb further away from the wrong end of the table.
An early home corner was dealt with by Pearson, before another one was claimed by McKeown.
A foul by Disley on Shaun Densmore gave Altrincham a free kick in a dangerous position on six minutes but Simon Richman’s header from it went over the bar.
The hosts were on top in the early stages and they won another corner on nine minutes but it did not cause any problems for the Town defence, as Nsiala cleared and was then fouled.
A second foul by Disley earned him the first yellow card of the game, before a deflected shot gave Altrincham their fourth corner, which was cleared from danger.
Town’s first attack of note came on 14 minutes and saw Magnay find Arnold, who shot at home keeper Stuart Coburn.
Another Town attack was in progress when a smoke bomb was thrown onto the pitch from the away section and the game was briefly stopped.
After play restarted, a Grimsby corner from Arnold was cleared back to him and his second cross saw a Pearson header saved by Coburn.
A foul by Nsiala gave the home side a free kick inside the Town half but they were unable to turn it into a goalscoring opportunity as the ball from it was too strong and went out for a goal kick.
Town had come into the game after Altrincham’s quick start and their next opportunity came when Neilson beat his man and tried a shot from outside the penalty area that was held by Coburn.
Another effort by Neilson, this time on the volley, bounced in front of the keeper before he again managed to stop the ball.
Parslow fired a shot over the bar on 38 minutes after Magnay’s cross had been headed clear as far as the York City loanee.
Pell struck an effort off-target, before the hosts won a corner at the other end which turned into another after a block by Disley. This time, the danger stopped when Neilson was fouled.
A header from Disley was caught by Coburn after a cross by Magnay in the last minute of the half.
One additional minute was then signalled and with no further chances, the game remained goalless at the break.
No substitutions were made before the restart and an early Thomas cross sailed out for a goal kick, before Coburn caught a header from Disley.
Altrincham’s first opportunity of the half came on the break four minutes in, with Steven Gillespie missing the target with a shot from outside the box.
Chances were proving hard to come by in the early stages of the second period and James Lawrie was the next to fire off-target for the home side.
Brown replaced Pell and Clay came on for Disley as Hurst opted to change his midfield around on the hour.
A free kick given for a foul by Thomas then saw Altrincham go close when a header by defender Scott Leather had to be saved by McKeown.
Town had the ball in the net at the other end seconds later but there were to be no celebrations as John-Lewis’ header was ruled out for offside.
A double substitution by the hosts saw eight-goal top scorer Damian Reeves replace Gillespie and Sean Williams come on for Lawrie.
Town could have taken the lead when Neilson ran down the left and crossed for Arnold but his shot was well saved by Coburn, who turned the ball away for a corner.
Another corner followed soon afterwards and this time, the ball was eventually cleared.
But the Mariners did not have long to wait before they finally broke the deadlock with 67 minutes on the clock. ARNOLD picked the ball up and unleashed a 30-yard rocket which went across Coburn and into the back of his net.
Arnold won a corner as Town went looking for a second goal but the ball from the flag was cleared.
Ryan Crowther came on for Jake Moult for the hosts with 15 minutes to go and a home free kick three minutes later caused no problems as Densmore curled it into the side-netting.
Altrincham were having a good spell and they won a corner on 81 minutes, although the ball from the flag was headed wide.
Nsiala conceded another corner as the home pressure continued but Parslow cleared the danger, heading the ball away at the far post.
Neilson was replaced by Mackreth for the last three minutes of the game, before a cross from Peter Cavanagh was blocked for a corner by Pearson before it could reach Gianluca Havern.
The home pressure continued and the flag-kick quickly led to another corner, which was eventually dealt with by Parslow. Altrincham kept possession though and after the ball was worked back into the penalty area, it was turned into the net by LEATHER for 1-1.
Three added minutes were signalled by the fourth official and in the last of them, a foul by Nsiala right on the edge of his own box gave Altrincham the opportunity to win the game. Densmore stepped up to take the free kick but his shot narrowly cleared the bar.
That proved to be the last action of the game and the Mariners were forced to settle for just one point when they looked to be on course for all three.
They remain second in the Conference table though, ahead of their next game against Kidderminster Harriers at Blundell Park on Saturday.