Imagine that you’re swimming out into your local lake. You’re a capable swimmer, you know this body of water like the back of your hand, and you feel confident while athletically stroking through water enveloped by the early morning mist. You decide to dive underwater for a bit—you know, for fun—and that’s when you see it: the shadowy silhouette of something huge, rusted, and covered in seaweed. You panic, rise to the surface, and swim to the shore. Trembling. Terrified.