Grimsby slipped further down the League Two table after a third successive home draw.
But more importantly they missed there sixth penalty out of six attempts and this is clearly giving manager Russell Slade grave concern.
Ironically Swansea's equaliser came from the penalty spot on 69 minutes from striker Lee Trundle.
For Grimsby Dean Gordon became the latest player to miss from 12 yards just three minutes into the second half.
The player who has the strongest shot in the team chose to place his shot but Swansea's Willy Gueret went the right way and pushed the ball out. The penalty, given for a foul on Grimsby striker Michael Reddy by Gary Monk resulted in Michael Reddy being carried off with an ankle injury which required three stitches.
Sub Colin Cramb came on for Michael Reddy and headed home a Gordon cross on 56 minutes to put Grimsby in charge.
But when a cross came into the Grimsby box on 69 minutes Grimsby defender Robert Jones was ruled to have fouled Swansea sub Kevin Nugent and Swansea earned their point.
There were chances at both ends, but a draw was probably a fair result in a game that only sprung to life after half-time.