Cheered on by thousands of fans brandishing inflatable haddock, Grimsby aim to catch another big fish when the fourth-tier minnows face Brighton in their first FA Cup quarter-final for 84 years on Sunday.

As unfashionable underdogs from a provincial town on England's east coast, Grimsby's FA Cup adventure is the perfect encapsulation of the competition's appeal to football romantics.

The Mariners, who last played in the top flight in 1948, are languishing in the lower reaches of League Two after winning promotion via the National League play-offs last year.

The lowest-ranked side left in the FA Cup have defied the odds to reach the quarter-finals, becoming the first team in the competition's history to beat five clubs from higher divisions in a single campaign.

Paul Hurst's men eliminated three sides from League One and Championship promotion chasers Luton before their stunning 2-1 win at Premier League side Southampton in the last 16.

Grimsby are only the sixth team from the fourth tier or below to reach the last eight since the introduction of the Fourth Division in 1958-59, and only the second since 1989-90.

The fairytale run has been a welcome fillip for a town that has fallen on hard times in recent years.

Located on the south bank at the mouth of the Humber, Grimsby's proximity to the North Sea once made it one of the world's biggest fishing ports.

In its heyday in the 1970s, around 400 trawlers were based in the port of Grimsby, but by 2013 that number had plummeted to just five.

The collapse of Grimsby's fishing industry led 70 percent of the town's 90,000 population to vote to leave the European Union in 2016.

Fishermen had complained about regulations imposed by the EU, but Grimsby came in for scathing criticism when a local business group lobbied to avoid tariffs, customs and the other burdens of leaving the Union.

Cod Almighty

Grimsby's unwitting roll as a Brexit bellwether has come to define the town's decline.

Against such a bleak backdrop, it is no wonder the locals have embraced the positivity provided by their unexpected FA Cup success.

Over 4,500 Grimbarians -- as the town's citizens are known -- will travel to Brighton armed with thousands of inflatable fish.

Ever since Grimsby played then FA Cup holders Wimbledon in the fifth round in 1989 -- at the height of the trend for fans taking inflatables to matches in England -- Mariners supporters have proudly displayed the 'Harry the Haddock' blow-up fish on big occasions in tribute to their fishing heritage.

Grimsby fans also run a fanzine called 'Cod Almighty', so when Southampton tried to ban the iconic inflatables under Premier League rules, the subsequent outcry quickly forced them to relent.

That set the stage for a surreal post-match scene when Grimsby defender Anthony Glennon donned a fish mask to join fans celebrating their shock victory with shoals of the plastic haddock.

Grimsby's memorable triumph even reached British Parliament, where Prime Minister Rishi Sunak, a noted Southampton fan, offered his congratulations, saying it "pained" him to see his club beaten, but he "had a new team to support in the cup".

Now they are dreaming of repeating their aquatic celebrations at the Amex Stadium this weekend in the club's first FA Cup quarter-final since 1939.

But Brighton, currently seventh in the Premier League, will pose a formidable barrier to Grimsby's hopes of adding to the two previous FA Cup semi-final appearances in their 145-year history.

"We know how difficult it is going to be, but it will be a fantastic occasion and we've got to try and enjoy it as much as we can," Hurst said.

"Maybe it's time for me to start worrying about what we have to face!"