Ok

the deeper this iceberg, the more obscure

The idea is the entire image represents ALL knowledge about a subject. From there, parts of the iceberg are organized into "tiers" to categorize the knowledge. A common categorization is to organize information from top-to-bottom in order from "what most people know" to "fringe, unproven conspiracy theories". This makes sense for the iceberg metaphor: the tip of an iceberg is the part you can see from a ship. Most people also know that a big part of the iceberg is underwater. But only people with very specialized equipment can actually go into the ocean and see just how deep an iceberg is to get the whole picture. Sometimes people make the image even deeper