99% of internet travels in cables that are underwater in the ocean.
You can access the interactive map here via WeForum.org. Below is a snippet:
Have you ever wondered how internet traffic flies around the world? 99% of it travels through cables under the sea. That’s your internet telephone conversation, your instant messages, your email and your website visits, all making their way beneath the world’s oceans.
The reason is simple: in recent years, data has traveled through fiber optic cables. These are much faster and cheaper than trying to bounce messages off satellites and through the airwaves. But we can’t lay them all across our increasingly congested ground, nor can we realistically build telegraph cables to stretch over the Atlantic Ocean.
The miles and miles of cables, which are roughly the size of a garden hose, carry internet traffic at the speed of light. They can carry so much traffic that fewer than 300 cable systems transport almost all internet traffic around the world.