A much-improved performance by the Lilywhites couldn’t stop them slipping to their fifth consecutive defeat.
Two second half goals bagged the points for the visitors, who have been occupying a top-four place for most of the season.
Town will be encouraged by the way they competed against one of the league’s top sides, but their hopes of getting something out of the game took a massive hit when they lost the services of the injured strike pair of Mark Lovelace and Michael Gardner.
Although they bossed large chunks of the match in terms of possession, they failed to break down a back four, marshalled by the experienced John Toyne.
And when Gardner limped out of the action on the hour, you had to wonder where the seasiders’ goals were going to come from.
Lovelace had already retired with a hamstring injury after just 12 minutes.
Grimsby had keeper Peter Garnett to thank for their clean sheet at the break. One save from a Max Foreman shot was particularly outstanding. He also denied Gardner and Lovelace during two separate raids.
At the other end Ashley Bentley had a relatively quiet half as Town looked solid following the return of Dean Seiner to the back four.
But the defence was caught sleeping within a minute of the restart. Borough broke down the right and Mark Carroll crossed for James Deeming to tap in at the far post.
Town were justifiably despondent, having enjoyed the lion’s share of possession, but chances to equalise were drying up, save for a Gardner effort he created for himself, which Garnett did well to keep out.
To their credit the home side continued to press and Seiner was pushed up in a bid to rescue a point.
Man of the match Dan Tuplin and Matt Veall combined well to keep the Grimsby midfield quiet, while new signing Shaun Boothby caused the visitors some concern with his darting runs.
However, the Lilywhites were dealt a cruel blow when Kurt Grantham beat the offside trap, rounded Bentley, and rolled the ball into an empty net with virtually the last kick of the game.
Skegness Town: Bentley, S Trestrail, Seiner, Nicholls, Cartwright, Foreman, Boothby, Tuplin, M Lovelace, Gardner, Veall, Miller, Johnson, Clark.
Tonight (Wednesday) Town travel to Fulstow to take on in-form CGB Humbertherm (kick-off 6.30pm). On Saturday they are at home again when Hykeham Town travel to Burgh Road for a 3pm kick-off.