Is worldbuilding like an iceberg?

NK Jemisin, Brandon Sanderson, and YouTuber The Closer Look all liken worldbuilding to an iceberg. The tip of the iceberg you could call the "here and now" story elements: places, characters, motivations, tension, plot: the things that propel the story and hold the reader's attention. The bigger underwater part is history, backstories, metaphysics, religions, cultures (HBMRC). Without these things, the here and now story elements wouldn't fit together⁠—not well, at least. That's the craft of worldbuilding.

The metaphor is appealing, but is it true? To what extent is "invisible" worldbuilding truly invisible?

I've written before how it's wise to leave details up to readers' imagination. Give too much detail, and you run the same risk as movie adaptations: depicting a setting or character differently than how the reader imagined it. Describing a character as handsome allows the reader to picture whatever he wants depending on his tastes; describing the character's features in detail⁠ to the exclusion of others would limit the effect of that attribute. Plus, as a general rule you should err on the side of brevity.

HBMRC gainsays this principle. The reader may think it's there under the surface, holding up the tip of the iceberg, but it's really not. It's not anything until the writer breathes it into existence with words on the page.

Sure, if you take a snapshot of a conflict, it will be stripped of most subtlety and subtext. You'll see the the tip of the iceberg, from whose detail you can only hope to infer what holds it upright. But stories are not snapshots. Exposition can interrupt at any moment to clue the reader in as to why and how the here and now came to be. It's not so much invisible as handled deftly since it's not as pressing as the here and now.

Some examples:

• The Battle of Gettysburg lasted 3 days, but you can go back months to trace the causes of the battle, and decades to trace the causes of the Civil War. To tell the story of that battle to someone who never heard of it, you wouldn't leave all that out, but you wouldn't give it proportional time either.
• The Abyss is a great story. It takes place over a handful of days, but Orson Scott Card's novelization goes years into the past to explore the main characters' backstories. Although the movie couldn't devote that time because it's a different medium, you can still understand the characters and their primary traits through their actions. The B plot tension derives from Bud and Lindsey's failed marriage, and the movie makes a point of reminding you of this early and often.
• Inception has a very complex setup. The technology of shared dreaming has to be explained, and Cobb's, Sato's, and Fischer's backstories have to be explained for the movie to make any sense. That's why the main job doesn't begin until almost an hour into the movie. The worldbuilding isn't hidden. The filmmakers put it front and center because without it you'd be lost.

In conclusion, I don't believe the iceberg metaphor best describes the reader's experience of worldbuilding. The anticipation of HBMRC can sustain for a time, but not to the end of the story. The writer eventually must support the tip of the iceberg with specifics that are inherently visible to the reader. The method of worldbuilding, like writing anything else, is a matter of craft.

As always, let me know what you think in the comments. If you like hard sci-fi, check out my books Seeds of Calamity and Tendrils to the Moon. You can find extended previews for each here and here.