Fear of the unknown is at the root of my favorite new horror movie of the last year or two, The Descent. When I started thinking about this essay, I expected to write about The Descent. It deserves to be written about — it’s nuanced, intense, and so scary that after seeing it I used my cell phone as a flashlight to illuminate the far corners of my bedroom.

But despite The Descent’s use of a fear of the unknown, I knew I’d be writing about something else when I saw this picture:

That’s a hole in the floor of the ocean, featured on a site with a collection of pictures of, no snickering please, giant holes.

No matter how scary I think The Descent is – and that’s pretty scary – this picture is far scarier, this goes to the gut, the viscera of what makes the unknown scary.

That hole, called the Great Blue Hole, is off the coast of Belize. It’s 1,000 feet wide and 400 feet deep.

I think this hole, especially seen from this perspective, is scarier and encompasses fear of the unknown better than any movie I can imagine.

I’ve always found large bodies of water, especially those so dark that you can’t see what’s beneath you, somewhat frightening. It’s a child’s fear, but even as an adult every so often I’ll swim in a lake with forests of long weeds growing from its floor that invariably brush my legs or wrap lightly around my feet. At the moment of their touch, a queasy electric charge shoots through my body, lighting my stomach up with fear.

It’s irrational, of course. What’s in a lake that’s going to harm me? A monster? Of course not, but those dark waters beneath me could contain anything – anything – and I wouldn’t know it.

I look at that picture of the Great Blue Hole and I imagine swimming or sailing over it. I imagine cruising along in the beautiful blue water, seeing the ocean floor beneath me and not worrying at all about unknown depths. But suddenly the ocean floor has fallen away profoundly, deeply.

And nothing happens. That’s surreal, it violates our understanding of how the world works. When a hole opens up below you on land, gravity pulls you down into it. When you see a hole below you, you should fall. Instinctively, in your pre-human, lizard brain, you know you should be falling and you panic. But you don’t fall in water. The world has fallen away from you and you haven’t followed it.

More than that, a hole like this feels wrong. These geological features occur, but we don’t expect them. And if something so profound as the ocean floor – the very skin of the earth itself – can collapse like that, then what could be in the hole? If the world contains mysteries deep enough to contain that hole, then what does the hole contain?

These pictures are beautiful, of course, but they’re also awe-inspiring. And that’s just the right word: awe. Dictionary.com defines it as:

an overwhelming feeling of reverence, admiration, fear, etc., produced by that which is grand, sublime, extremely powerful, or the like