The modern internet feels wireless, instant, and invisible. A video call crosses oceans without a second thought. A cloud server responds faster than a local hard drive once did. Yet beneath that smooth digital surface lies one of the most physically demanding engineering systems ever built: undersea internet cables. Stretching across thousands of kilometers of ocean floor, these cables quietly carry nearly all international data traffic, enduring crushing pressure, corrosive saltwater, shifting seabeds, and human interference.