A tunnel linking Wales and Ireland has been proposed by a think tank, but the approximately $23.5 billion (£15bn) price tag may be prohibitive.
The tunnel would connect Dublin and Holyhead, Anglesey in Wales, a major Irish Sea port serving Ireland. The project would take to the end of the century to finish.
However, the Taoiseach's office in Dublin has said the cost of tunnel could make the project unrealistic.
The underwater tunnel along with other ambitious infrastructure developments are proposed in the Vision 20:35' Cymru Wales report by the Chartered Institute of Logistics and Transport (CILT). Other improvements include electrified railways cutting travel from London to Cardiff to an hour, and innovative transport technology which would spread throughout Wales over the next two decades.
Professor Stuart Cole, of the Transport Research Centre at the University of South Wales, does not believe the cost would be an issue.
“We're talking about something like £15bn [$23.5 billion],” he said. “Something like the cost of HS2 [high speed rail line] between London and Birmingham.
"So we're not talking about a massive amount of money in the world of governments.
"Also, much of this money would come from the European Commission," he added.
Dr Andrew Potter, Chair of CILT Cymru Wales, said: “As an essential part of the economy, it is hoped Vision 2035 provides a long-term view of transport in Wales.
"By thinking now about the opportunities and challenges ahead, better solutions can be found that make a real difference to passengers and businesses alike."