Morecambe suffered back to back away defeats in League Two after defeat against the Mariners at Blundell Park.
Morecambe took the lead after just 67 seconds.
Michael Mellon won possession after a loose Grimsby defensive header, he played it to JJ McKiernan who released Adam Mayor, and he slotted into the bottom left corner to give the Shrimps the perfect start.
The Shrimps came close to a second on 13 minutes when Jordan Slew played Mayor through once more, but Harvey Cartwright was quick off his line to smother the danger and deny Mayor a second.
At the other end, Adam Smith was called into action to palm behind a curling effort from Otis Khan, before denying Khan with his feet, the ball deflecting onto the post.
Grimsby continued to press but couldn’t find an equaliser, with the Shrimps heading into half time with their noses in front.
Morecambe made a double substitution at half time but it was the hosts who started the second half the brighter, and were soon ahead thanks to a quick fire double.
In the first minute after the restart, Anthony Glennon ran at the Morecambe defence before Danny Rose struck first time, forcing Smith to be at full stretch to deny him.
The equaliser came soon after.
A corner was swung into the near post, Smith spilled the ball from his grasp, and Rose was in the right place at the right time to prod home from close range.
The Mariners then took the lead less than two minutes later through Kieran Green, who reacted quickest to Rose’s header down and converted from close range.
Jordan Slew fired over the angle for Morecambe, before the hosts went down the other went and netted their third of the afternoon through Reikell Pyke, who latched onto a through ball from Glennon and finished at the back post.
An incredible piece of goalkeeping on 63 minutes denied Grimsby a fourth. The ball fell to Pyke who managed to turn and shoot at goal, but Smith made himself big to keep the ball out.
Morecambe tried to reduce the arrears, with Slew’s effort well turned behind by Harvey Cartwright at full stretch, before the Shrimps got one back with four minutes to go.
Eli King slipped in Slew on the right side of the area, and his square ball was forced home by JJ McKiernan.
In the first of six added minutes at the end of the 90, Eli King received the ball at the left-hand side of the opposition box, he struck at goal but the legs of Cartwright did enough to keep the ball out.
Substitute Ethan Walker sent an effort wide, and Yann Songo’o headed straight at the keeper in added time, as Derek Adams’ men suffered just their second defeat in ten games.
Morecambe remain in the League Two play off positions, in seventh place in the table.
Grimsby Town: Cartwright, Glennon (Hunt, 80’), Green, Rodgers, Holohan, Pyke (Wilson, 80’), Khan (Eisa, 71’), Andrews (Clifton, 58’), Mullarkey, Maher, Rose ©.
Subs not used: Eastwood, Waterfall, Hunt, Conteh.
Goals: Rose (47’), Green (49’), Pyke (59’).
Bookings: Khan, Holohan, Hunt.
Morecambe: A Smith, Tutonda (Walker, 88’), Bedeau © (Davenport, 88’), Bloxham (Songo’o, HT), King, Mellon, McKiernan, Mayor, Senior, Slew (Melbourne, 90’), Connolly (Rawson, HT).
Subs not used: Pedley, C Smith.
Goals: Mayor (02’).
Attendance: 5,939 (139 away).