Archaeologists working on a gas pipeline near Milford Haven in Pembrokeshire have unearthed what they believe to be a 3,400-year-old canoe.
Work has stopped on a section of the pipeline near St Botolphs to allow the Bronze Age oak relic to be recovered.
It is the first such discovery in Wales and only 150 exist across Europe.
Senior archaeologist Neil Fairburn said: "You could never have expected to find anything like this in this small wetland area, it's just awesome."
The team has also found evidence of a small settlement, a small amount of property and other items, such as polished stone rings.
Mr Fairburn, who works for the National Grid, said: "Everybody here is excited and it's unlikely they'll ever work on anything like this again."
It was found six weeks ago less than a metre below the surface in a marshy area of land, but archaeologists have only just had it confirmed what the find was. Work was stopped immediately.
A fragment was sent to experts in Miami, who radio carbon dated it to 1,420 BC.
The canoe is carved from a single trunk of oak, and measures 4.5m x 0.9m (15ft x 3ft).
It is being kept continuously wet to prevent it from rotting.
Mr Fairburn added: "The wet conditions have provided beautiful preservation conditions for the wood.
"If the gas pipeline had not been coming through here we would not have this."
It will take another two weeks before the team is ready to move the canoe, which will be handed over to the National Museum of Wales.
Contractors have been moved to work on other parts of the route, which will run the breadth of Wales.
The natural gas pipeline will link two liquefied natural gas (LNG) terminals at Milford with the UK's gas supply.
There have been protests against the LNG and pipeline project on safety and environmental grounds - and this was not the first time work had been stopped after an unexpected discovery.
Earlier this year work was stopped on a section of the route at St Clears after a human thigh bone and other fragments were unearthed by contractors.
The remains were later identified as specimens used by the medical profession or students.