The National Telecommunications Authority in Majuro has shifted all phone and Internet communications from the cable to satellites, reducing the available bandwith by 97 per cent.
Since the repair work began on Wednesday, Internet access has been limited to email only for the 53,000 residents in the western Pacific nation.
All social media sites have been closed, except for selected business customers, and it is impossible to stream movies and videos.
"It gives us a new evaluation of what the Internet means to us," said Jerry Kramer, the chief executive of Pacific International, the Marshall's largest construction company.
The finance ministry was reported to be struggling to process the government payroll with access to its web-based payroll processing system curtailed.
The repair work is expected to be completed by January 8.