The 'Saltees Quest' Beam-Trawler picked up a strange item while fishing off the coast of Dunmore East on Friday.
Fishermen say it looks like it could have been some kind of anti-aircraft gun from a submarine from approximately the 1940s.
Ballistics are expected to carry out investigations on it in the coming days, and James Duffin who is Skipper on the trawler said the crew are delighted with the discovery.
"Friday we were towing and we picked up a heavy object in the gear when we hauled it up we thought it would be a large stone or something like that.
"When we topped up the gear we could see immediately that all the brass was shining off the gun. There are around 500 kilos of solid brass at the mounting of the gun.
"We believe it's an anti-aircraft gun from a submarine," James said.
Gardaí in Dunmore East inspected the object over the weekend, and Passage East native James said that tests will have to be carried out.
"It's definitely 70 or 80 years old and we're going to be doing a bit of history on but first we have to find out the group that are doing tests on it to see it's live or not.
"Hopefully then we will be able to send it to a museum. There still is a possibility it could be live but it's very doubtful unless they had it loaded.
"The boat would only use that when it's on the surface for anti-aircraft so it would have been loaded [at some stage] but we don't know whether it was taken down by a plane, or ship we don't know but hopefully, we'll soon find out," the Saltee Quest crew-member said.
The job of a skipper isn't an easy one, and if anything - James said making a discovery like this certainly is a big lift for all of the crewmembers.
"We'd spend nine or ten months of the year at-sea so we'd be into all of these sorts of items that you might come across. We're fisherman but we're also trying to better the job for ourselves.
"We're fishing for plastic and we bring it ashore - 'Fishing for Litter' - is a big thing in Ireland and we bring a tonne of litter in every week and we're cleaning the oceans.
"It is nice to see these things coming up and you would be very interested in and trying to find out information because this gun could have taken down many ships and perished many men," he said.
The past few months have been difficult for the fishing industry, with the prices falling, the impact of the pandemic and the impact of Brexit just a few of the difficulties they've had to face.
"With the Covid and all it's been a tough year for every fisherman with prices and the market - we're all in the one boat when it comes to this.
"All we can do is keep our heads down as we always do and keep going until things get better," James said.