The "Undersea Internet" refers to a network of cables that run along the ocean floor, connecting different continents and countries. These cables carry the majority of the world's internet data, allowing for communication, streaming, and online services across vast distances. These undersea cables are made of fiber optics, which transmit data as light signals. They are crucial for global connectivity, enabling everything from social media to e-commerce. The cables are laid by specialized ships and can stretch thousands of miles, making them essential for the modern digital world.