Inside the world’s deepest and longest subsea road tunnel

It’s cold, it’s very, very noisy, and—if I can be quite honest with you—I’m not feeling super relaxed. I’m currently around 300 meters, or 1,000 feet, beneath the North Sea, in a dark, dank cave. And I am increasingly aware of the pressure from millions of tons of seawater just above my head, pushing down with a force of more than 500 pounds per square inch.