The game was played on a bumpy pitch with a high swirling wind, but this in no way excused Notts County's lamentable performance in the first 45 minutes.
Grimsby toyed with the home side and ultimately paid the penalty for not making their superiority count.
Despite plenty of possession, only once in the opening half did they seriously extend Notts' keeper Kevin Pilkington, who excelled by tipping over a close-range header by Ciaran Toner.
Some County fans booed their team off the field at half-time, but within minutes of the restart it was obvious that strong words in the dressing-room by manager Steve Thompson had worked wonders.
Jay Smith was immediately in the picture with a rasping volley, which Phil Barnes turned round his left-hand upright.
Yet, when County broke the deadlock in the 52nd minute, there was an element of good fortune about it.
Lawrie Dudfield's effort was sliced past his own goalkeeper by Grimsby defender Tom Newey, who otherwise produced an immaculate display.
The points, and a double for County, were only sealed four minutes from time with a superb breakaway goal. Substitute Andy Parkinson, formerly with Grimsby, outpaced John McDermott and squared the ball for Jay Smith.
Smith's first effort came back to him off the keeper's legs and, at the second attempt, he made no mistake.
There was uproar in stoppage time, when for a harmless-looking challenge, Notts' captain Jason Lee was cautioned for the 18th time this season in his second game back from a three-match ban.