Conor Wilkinson’s 5th minute strike had got Orient off to the perfect start, however they trailed at the break thanks to goals from Luke Waterfall and George Williams.
Substitute Jordan Maguire-Drew looked to have rescued a point with a superb individual strike, but Montel Gibson’s 90th minute penalty spot kick sealed the win for the Mariners.
Ross Embleton made four changes from the mid-week defeat at Walsall. Two notable alterations saw Dan Happe and Ruel Sotiriou return from suspension and international duty respectively to take their place in the starting eleven.
Seeking to make amends for the loss last time out, the O’s made an electric start in E10. Fresh from his exploits with the Cyprus U21’s, Sotiriou burst through the centre of the pitch and played a ball into the path of Wilkinson. The forward then confidently smashed the ball home at the near post to give the O’s an early advantage.
The Mariners retaliated strongly and eventually bagged an equaliser in the 22nd minute. Lawrence Vigouroux did well to initially turn Matt Green’s effort behind for a corner, but the Chilean was powerless to prevent Waterfall heading in from the resulting corner.
Things went from bad to worse for the O’s ten minutes later. Williams beat the offside trap to latch onto Owen Windsor’s through ball and slotted home to give the visitors the lead.
Orient responded with a spell of measured, controlled possession, but were unable to create any clear chances of note meaning they trailed at the break.
The first chance of the second half fell to the O’s, Wilkinson fired a low right footed cross into the feet of Danny Johnson, however Orient’s in-form man was forced to settle for a corner as his effort deflected behind.
Looking to get back into it, Embleton made his first substitution just after the hour mark; Wilkinson the man to make way for Jordan Maguire-Drew.
A second switch soon followed, this time Jamie Turley was replaced by Jobi McAnuff in an alteration that saw Craig Clay move into the right back spot.
Grimsby could have had a third in the 69th minute. Mattie Pollock struck the base of the post after connecting well with Terry Taylor’s set piece.
But it was the O’s who would be the next side to find the net. Happe sprayed a lovely cross-field pass out to the substitute, Maguire-Drew. What followed was a moment of genius. The winger shrugged off his marker, cut inside and unleashed an unstoppable arrow into the far corner to draw his side level with 25 minutes to play.
Immediately after the goal, Mariners defender, Pollock was left cursing the woodwork once again when his lofted header rattled the crossbar.
As the clock ticked into the final minute, Ian Holloway’s side were awarded a penalty after Clay brought down Windsor in the box. Montel Gibson made no mistake from the spot to put his side in front.
The O’s didn’t give up though and deep into stoppage time they were robbed of the chance of an equaliser. Johnson’s pull back appeared to strike a Grimsby hand in the penalty area, but referee Tom Nield saw nothing doing and waved away appeals, before blowing the final whistle shortly after.
ORIENT: Vigouroux, Akinola, Turley (McAnuff 67”), Happe, Brophy, Cissé, Clay, Wright, Wilkinson (Maguire-Drew 62”), Johnson, Sotiriou
SUBS: Sargeant, Ling, Widdowson, Coulson, Dayton
BOOKED: Wright, Maguire-Drew, McAnuff, Clay
GOALS: Wilkinson 5”, Maguire-Drew 74”
GRIMSBY: McKeown, Hendrie, Preston, Rose (Morton 46”), Waterfall, Green (Edwards 62”), Windsor, Williams (Gibson 69”), Clifton, Pollock, Taylor
SUBS: Battersby, Tilley, Starbuck, Idehen
GOALS: Waterfall 22”, Williams 32”, Gibson 90”
REF: Tom Nield