Grimsby Town came from behind to score five goals and record a big win over previously unbeaten Port Vale at Blundell Park.
In warm conditions, the visitors took the lead through David Worrall but held it for just seven minutes before Jordan Cook equalised.
Moses Ogbu's first goal for the club put the Mariners ahead six minutes after half-time and Matt Green looked to have made the points safe with a third goal.
Centre-back Nathan Smith got the visitors back into the contest when he made it 3-2 but late goals for Luke Watrfall and James Hanson put the gloss on a great home victory.
Cook replaced Sebastian Ring in the only change to the Town team that started the 2-2 draw with Colchester United in midweek.
That meant Elliott Hewitt moved to right-back and Luke Hendrie switched to the left as Harry Davis and Waterfall continued as the two centre-backs in front of goalkeeper James McKeown.
Cook lined up alongside Jake Hessenthaler and Elliott Whitehouse in midfield, with Green, Hanson and Ogbu in attack.
The Grimsby substitutes were Sam Russell, Ring, Charles Vernam, Max Wright, Mattie Pollock, Harry Cardwell and Harry Clifton.
Port Vale travelled to Cleethorpes looking to extend an undefeated start to the season that had seen them draw their first three games before beating Forest Green Rovers in midweek to claim their first victory.
Hewitt was given an early warning by the referee after a foul on Tom Conlon, before the first shot of the game on five minutes saw David Amoo fire straight at McKeown.
Ogbu set off on a run through the middle on nine minutes after Hanson had won the ball in the end but after reaching the edge of the box, the striker appeared in two minds as to whether to cross or shoot and sent it past the far post for a goal kick.
A foul by Hessenthaler gave the visitors a free kick on the right three minutes later and from it, they took the lead. Scott Burgess sent the ball into the danger zone and after Town failed to clear their lines, WORRALL pounced to bundle it into the net from close range.
Hanson was fouled by James Gibbons as Town looked to respond but Hessenthaler's free kick from midway inside the Port Vale half was cleared.
Another free kick soon afterwards was played low to Green and his cross was put behind for a corner on the right. Waterfall headed it towards goal and as the visitors cleared, Cook was caught by a high foot on the edge of the penalty area. Ogbu touched it to COOK and he drilled a low shot into the corner of the net to make it 1-1.
Ogbu almost had an opening on the edge of the box after a good touch by Green, before Waterfall let fly from distance soon afterwards but only found the empty section of the Osmond Stand.
At the other end, Worrall shot just over the bar from 20 yards after the away side were given space in a dangerous area.
A Vale corner on 36 minutes was cleared, then a short stoppage came after Davis was fouled by Worrall as both chased a ball down the away right. The defender stayed down but was passed fit to play on after receiving treatment.
Two added minutes were played at the end of the first half and with no further chances for either side, the scores remained level at the break.
Davis had continued to feel the effects of the shoulder injury he picked up in the challenge with Worrall and was replaced by Pollock before the restart.
Town started the second half brightly and Ogbu went close to giving them the lead two minutes in but saw his 20-yard volley narrowly clear the bar.
Green won a corner on the right on 50 minutes and after it was half-cleared to the edge of the box, Cook fired over the bar.
The Mariners finally got their reward for a good start to the half a minute later when they got themselves in front for the first time in the game. OGBU was the man on-target, smashing the ball into the net after finding space inside the box.
Worrall was booked for a foul on Ogbu which stopped the attacker from breaking clear down the right.
And on 56 minutes, Town established a two-goal cushion as Hanson flicked a header on for GREEN, who ran though and kept his balance to slot past visiting keeper Scott Brown.
Mark Cullen was sent on in place of Ryan Lloyd for Port Vale after the goal, before Clifton replaced Green in Grimsby's second change on the hour.
The visitors were back in the game soon afterwards as they reduced the deficit to one goal when SMITH beat the dive of McKeown and found the far corner of the net from the edge of the area.
Tom Pope replacd Ritchie Bennett to give the away side extra attacking threat but it was the Mariners who created the next good chance. Cook took the ball through the middle before finding Ogbu, who in turn passed to Hessenthler on the right. The midfielder's cross was met by Cook but his header went over the bar.
Hewitt was fouled by Luke Joyce on 72 minutes but the referee allowed play to continue and Hanson cut in from the left but shot over the bar. Joyce was then shown the yellow card.
Worrall was replaced by Ryan Campbell-Gordon in Port Vale's final substitution with 13 minutes to go.
Ogbu did well to win a corner two minutes later on the right and from it, the Mariners finally put the result beyond doubt. Hessenthaler played the ball short to Hewitt and his cross was met at the far post by WATERFALL, who powered a header home.
Wright replaced Whitehouse with a little under 10 minutes to go and the substitute was heavily involved as the Mariners scored a fifth goal. Wright's pace saw him get onto a ball down the left and after he pulled it back for HANSON, the striker steered it into the net.
Five minutes of added time passed before the Mariners and their fans were able to celebrate their win, as an excellent second-half display was rewarded with all three points.
Town are next in action on Tuesday, when Macclesfield Town visit Blundell Park in the second round of the Carabao Cup.
1 James McKeown (C)
22 Elliott Hewitt
2 Luke Hendrie
6 Luke Waterfall
4 Harry Davis
8 Jake Hessenthaler
11 Jordan Cook
10 Elliott Whitehouse
9 James Hanson
7 Matt Green
20 Moses Ogbu
23 Sam Russell
25 Matthew Pollock
21 Sebastian Ring
15 Harry Clifton
19 Max Wright
17 Harry Cardwell
18 Charles Vernam
1 Scott Brown
2 James Gibbons
3 Adam Crookes
5 Leon Legge (C)
15 Nathan Smith
4 Luke Joyce
19 David Amoo
7 David Worrall
10 Tom Conlon
22 Ryan Lloyd
21 Richie Bennett
30 Jonny Maddison
23 Ryan Campbell-Gordon
18 Callum Evans
6 Kieran Kennedy
20 Scott Burgess
13 Mark Cullen
9 Tom Pope
Referee: Will Finnie
Attendance: 4,290 (246 away)
Next Up: Macclesfield Town (H)