How big a deal is Microsoft and Facebook's underwater Internet cable?

Microsoft and Facebook are joining together to build an underwater Internet cable across the Atlantic Ocean.

The cable, known as MAREA, or "tide" in Spanish, will connect hubs in northern Virginia and Bilbao, Spain, helping the tech giants increase their capacity to carry data for a growing number of online customers and businesses that use their services.

By designing and creating their own private networks to move massive amounts of data necessary to run popular services such as Facebook Messenger, WhatsApp, Microsoft's Bing, and Office 365, the tech companies are increasingly expanding into an area traditionally dominated by telecom companies.

The project, which comes in the wake of a similar effort by Google in the Pacific, is particularly intended to reduce latency, or the time it takes information to get from data centers to its destination.

"In order to better serve our customers and provide the type of reliable and low-latency connectivity they deserve, we are continuing to invest in new and innovative ways to continuously upgrade both the Microsoft Cloud and the global Internet infrastructure," said Frank Rey, director of global network acquisition at Microsoft, in a statement on Thursday.

MAREA, which is initially designed to carry data at 160 terabits a second, will be operated and managed by Telxius, an affiliate of the Spanish telecom Telefónica, the company says. The telecom will sell off unused capacity on the cable to other customers.

Construction on the cable that will stretch more than 4,000 miles, the first to connect the United States with southern Europe, will begin in August and is expected to be completed in October 2017.

A connection to Bilbao also opens up a pathway to expand Internet service to several regions of key interest to the tech giants, including Africa, the Middle East, and Asia, Najam Ahmad, Facebook's vice president of network engineering, told Wired.

Through its Project Natick, Microsoft also began experimenting with underwater data centers last year, testing a prototype on the sea floor for four months.

Underwater data centers, especially if they are powered by marine energy sources, are intended to greatly reduce the costs that come with cooling the racks of servers. By placing the centers underwater, the companies also hope to reduce the distance between connected populations.

The underwater networks are one of a slew of efforts by tech giants to provide Internet service across the globe, including Facebook's efforts to design Internet-delivery drones, a plan to use satellites in Africa, and Google's balloon-powered Project Loon.

Tech companies are also moving an increasing amount of data themselves. More than two-thirds of the digital data moving across the Atlantic is now running on private networks developed by tech firms, according to the research firm Telegeography. That's a significant increase from 10 percent a few years ago, Wired reports.

For Facebook and Microsoft, building its own networks also offers more freedom to use their own equipment rather than depending on technology provided by telecom firms.

"You're stuck with whatever system was built initially. And if there has to be an upgrade, all the partners in the consortium have to agree to that upgrade," Mr. Ahmad, the Facebook executive, told Wired.  "[The MAREA Project] gives us more control of our own destiny."

This report contains material from Reuters and the Associated Press.