Ian Holloway celebrated his 1,000th game as a manager in style by blowing away Grimsby courtesy of a Kabongo Tshimanga brace.
In gusty conditions Swindon were ahead after three minutes when a clearance got held up in the air, Tshimanga raced onto a header from Harry Smith and the ball broke for captain Ollie Clarke to slot in.
Smith should have doubled the lead seconds later but rattled the post and then fired the rebound over.
Before the break, Tshimanga gobbled up a poor defensive header which landed at his feet for him to thunder home.
The Peterborough loanee began the second half in menacing form, rattling the upright in the opening seconds.
After a handball in the away box Will Wright badly missed from the spot making it six botched penalties in the last seven for the Robins.
A Town break saw Clarke expertly feed Tshimanga who blasted into the roof of the net to make it 3-0.
The Mariners got one back from Danny Rose‘s penalty after a foul on former Swindon midfielder George McEachran.
Cameron Gardner then had his point-blank shot saved by Daniel Barden and Swindon held on for a crucial victory.
