Facebook and Microsoft have partnered on Marea, a project to build a new fiber optic cable that will run for 4,000 miles under the Atlantic Ocean between Virginia and Spain. Telefónica SA, a Spanish Internet service provider, joins them in the project. The fiber link, composed of eight pairs of strands, will be the highest capacity link across the Atlantic. Marea, the Spanish word for tide, is just the latest such project that Microsoft, Facebook, Alphabet, and Amazon have invested in to lower costs of moving massive amounts of data.

The Wall Street Journal reports that the Marea partners say the project will “help to lower costs, accelerate bandwidth rates and help accommodate the explosion of data use around the world.”

Microsoft executive Christian Belady adds that Microsoft also “wanted to build redundancy in its network and invest in an area where cables don’t run.” “We were looking for other places” away from New York, he said. “You want to make sure you have multiple paths. You can’t survive on one cable, or frankly two.”

Telefónica’s new infrastructure company, Telxius, will manage the trans-Atlantic link, but Facebook and Microsoft will handle their own dedicated fiber optic lines with the ability to upgrade the gear at both ends.

Analysis firm TeleGeography research director Alan Mauldin points out that only the biggest Internet companies can invest in these large underwater cable projects. The Marea partners would not reveal the cost, but Mauldin explained that trans-Atlantic cables “usually require more than $200 million to build.” Internet companies mainly build in “heavily trafficked Internet corridors” in Europe, the Americas and East Asia where they have data centers.

Google, a pioneer in 2010 when it teamed with partners to build a 6,200 mile connection across the Pacific Ocean, is now completing a second trans-Pacific cable and an Atlantic line from the U.S. to Brazil. Microsoft led the U.S. investment in the New Cross Pacific Cable to China and Amazon participated in the Hawaiki cable from Oregon and Hawaii to Australia and New Zealand.