Grimsby Town started 2021 with a narrow home defeat as Cambridge United held on for all three points at Blundell Park.
The Mariners fell behind after just four minutes when Adam May opened the scoring from the visitors' first attack.
And a confident Cambridge side doubled their advantage on 36 minutes when Paul Mullin struck.
Town came out fighting after half-time though and they halved the deficit through Elliott Hewitt's header.
The hosts piled forward as the clock ticked down but despite their pressure, they were unable to find an equaliser.
New Grimsby manager Paul Hurst's first-team selection of his second spell in charge showed two changes from the XI that began the goalless draw with Oldham in midweek.
One was enforced as Owura Edwards had been recalled from his loan by parent club Bristol City, while George Williams dropped to the bench as James Tilley and Kyle Bennett came into the starting line-up.
Sam Russell continued in goal as James McKeown continued his self-isolation period, with Luke Hendrie, Mattie Pollock, Luke Waterfall and Danny Preston forming an unchanged defence.
Filipe Morais, Danny Rose and Hewitt were the midfielders, with Tilley and Bennett either side of Matt Green in attack.
Joining Williams among the substitutes were Ollie Battersby, Joe Starbuck, Duncan Idehen, Harry Clifton, Ira Jackson Jr and Montel Gibson.
Cambridge were looking to get their promotion push back on track after losing five of their seven league games in December, although they had won two of their last four fixtures.
Mark Bonner's side were eighth in the table at kick-off and would look to the likes of strikers Mullin and Harvey Knibbs to fire them to victory.
An early free-kick from Bennett was comfortably cleared by May, before a second set-piece from the opposite flank produced the same result.
Cambridge went on to take the lead as a cross from Mullin on the right was not fully dealt with and MAY hit a shot from 20 yards which took a heavy deflection and beat Russell.
Another Town free kick came soon afterwards and this time it was Rose who lifted it into the box but nobody could get on the end of his delivery at the far post.
Hewitt was spoken to by the referee after a foul midway inside his own half on 10 minutes, before Green won a corner on the right as his low cross was blocked. Bennett's ball from the flag was not dealt with by the Cambridge defence and it fell for Pollock but his shot was blocked.
The visitors almost doubled their lead on 14 minutes when a good ball from Mullin picked out striker Harvey Knibbs, although Russell did well to block his shot and the rebound was also blocked for a corner.
Morais tried his luck from distance on 19 minutes but Cambridge goalkeeper Dimitar Mitov reached up to claim a comfortable catch.
The next opportunity for the Mariners was created by Bennett six minutes later but his 30-yard effort sailed just wide.
A cross from Morais on the right was headed clear, before another attacking move almost led to a shooting chance for Green but the ball was put behind for a corner, which was cleared.
A stoppage came when Cambridge right-back Kyle Knoyle went down with an injury on 33 minutes but he was passed fit to continue after receiving treatment.
Town had looked better in attacking areas since the goal but the away side remained comfortable in their lead and they made it 2-0 nine minutes before the break. MULLIN cut in from the right after a ball forward from Harry Darling and the striker unleashed an unstoppable shot from just inside the box that flew past Russell for his 20th goal of the season.
The Mariners looked to reduce the deficit before half-time but were unable to cause significant problems for Mitov and his defence.
Three added minutes were played at the end of the half and with no further chances, the visitors retained their two-goal advantage and remained in control at the break.
Gibson replaced Tilley for Town before the restart and the hosts were the first to attack, with the substitute heading over the bar after a cross from Hendrie on the right. Mitov required lengthy treatment after colliding with Gibson but was eventually passed fit to play on.
Bennett headed wide from a cross by Morais, then the Bristol Rovers loanee was involved again as he flashed a shot wide after a free-kick was given for handball.
The Mariners won a corner on the hour but Bennett's ball was headed clear. Town retained possession though and a follow-up delivery into the box from Pollock was also headed away.
A cross at the other end was cut out for a throw-in and the away side's next attack brought a chance as a slip let Luke Hannant in on the left. He pulled the ball back for Mullin but this time, the striker lifted his shot over the bar.
A corner from Bennett on the right was half-cleared and when the ball was played back in, Gibson was denied when his far-post header was brilliantly kept out by Mitov.
Hannant then hit the side-netting at the end of a Cambridge attack, when Mullin had been in place for a tap-in if the ball had been pulled back for him.
Clifton replaced Rose in the Town midfield on 70 minutes and two minutes later, the hosts were back in the contest as they reduced the deficit to one goal. A cross from Bennett on the left was met by HEWITT and his header looped into the net.
Joe Ironside came on in place of Knibbs in the Cambridge attack, before Pollock did well to win the ball ahead of Mullin and deny the striker another shooting chance, at the expense of a corner.
Williams replaced Bennett and Jackson came on for Green as Town made a double substitution with 11 minutes to go.
A quick break by the Mariners saw Morais make ground down the right before a Hendrie cross was headed behind for a corner. Robbie Cundy replaced Darling for Cambridge before it was taken, with Pollock's header deflected over the bar for another corner.
The home pressure continued as a cross from Clifton was headed out for another corner but this time, Morais' delivery to the near post was cleared from danger.
Mullin shot at Russell after good link-up play with Wes Hoolahan on the left, then Waterfall had to head the ball out for a throw-in after getting to it ahead of Ironside.
A cross from Hendrie was headed wide at the far post as the Mariners kept attacking in search of an equaliser with the clock ticking down.
They were given an additional six minutes to force a share of the spoils and a great cross from Morais to the far post had to be well-defended.
Hoolahan was replaced by Jack Iredale as the visitors looked to see out the game and hold on to their advantage.
Town piled the pressure on, aided by a string of corners, but they were unable to force a way through the Cambridge defence as the away side held firm.
The result, along with others elsewhere, meant the Mariners dropped into the League Twi relegation zone.
They are next in action on Saturday, when they travel to Port Vale.
23 Sam Russell
2 Luke Hendrie
3 Danny Preston
6 Luke Waterfall (C)
25 Matthew Pollock
22 Elliott Hewitt
18 Filipe Morais
4 Danny Rose
37 Kyle Bennett
7 Matt Green
21 James Tilley
13 Ollie Battersby
32 Duncan Idehen
15 Harry Clifton
29 Joseph Starbuck
10 George Williams
12 Montel Gibson
16 Ira Jackson Jr
1 Dimitar Mitov GK
2 Kyle Knoyle
11 Harrison Dunk
6 Harry Darling
5 Greg Taylor (C)
19 Adam May '
7 Luke Hannant
4 Paul Digby
14 Wes Hoolahan
26 Harvey Knibbs
10 Paul Mullin
25 Callum Burton
16 Robbie Cundy
17 Leon Davies
3 Jack Iredale
27 Ben Worman
9 Andrew Dallas
20 Joe Ironside
Next Up: Port Vale (A)