But veteran Darren Anderton gave the Cherries hope with a second goal and even then Bournemouth went down to ten men when defender Scott Guyett was sent off in the 82nd minute for a second bookable offence.
With Bournemouth now having all the play they drew level with two minutes left. Skipper Shaun Cooper's shot was diverted past keeper Phil Barnes by striker Lee Bradbury for his second goal of the game.
It was the lively Bradbury, back after suspension, who shot Bournmouth ahead on six minutes. Grimsby then made the most of the awful conditions to turn the game on its head by scoring twice in three minutes just before half-time.
Firstly midfielder Jamie Clarke cracked home a terrific shot and then skipper Ryan Bennett looped in a header to put Grimsby 2-1 up.
And when central defender Rob Atkinson headed in Nick Hegarty's corner on 61 minutes it looked all over for Bournemouth.
But with a two-goal lead, Grimsby showed alarming stage fright and once Bournemouth grabbed their second goal there was an inevitability about their equaliser.
It was good entertainment for an above average crowd but at the end it felt like a win for Bournemouth and a defeat for Grimsby.
The 12-point gap between the sides remains but Bournemouth were clearly the happier side on the long journey home